Home | Aquarium Set-up | More Decoration DIY: Materials and Aquarium Suitability

More Decoration DIY: Materials and Aquarium Suitability

The first two installations of our DIY blog series – “Adding a Personal Touch to You Aquarium Decor” and “Aquarium Decoration Ideas – Fish Bowl Designs & DIY” – seem to have gotten your creative juices flowing so we’re back with another entry. The most frequent questions we’ve gotten since then have been about the materials that you are looking to put into your aquarium so we’re going to break down some of the most popular materials that you’ve all asked us about. Remember, these are just some basic guidelines and you may need to test the piece you’re trying to use.



  • Choosing the right glue or adhesive for your purpose can make or break a project.

    Choosing the right glue or adhesive for your purpose can make or break a project.

    Cyanoacrylate Glue (“Reef Glue”, “Krazy Glue”, “Super Glue”) – These glues are some of the most common, especially among aquarists and reef hobbyists. They are effective with many different types of materials and are very strong, particularly when bonding plastic materials. They work well with reattaching coral frags that may have dislodged or fixing ornaments and they cure quickly. Most of them tend to turn milky-white if they are put into the water while the glue is still wet but they are otherwise safe for lots of applications.

  •  Silicone Sealant – Silicone sealants are usually used to fix the seams of an aquarium but they can also be used in assembling ornaments and pieces within the aquarium. It is usually available in black or “clear” (usually more milky blue-white, in my experience) and can be thicker that cyanoacrylate glue, but it is durable and more flexible once cured. Be sure to read the directions to make it easier to use and cure it fully before using it in your aquarium.
  • Epoxy – Epoxy is a two-part adhesive that needs to be mixed together to activate. Underwater epoxies usually look like a putty with an outer coating over a contrasting center and are commonly found in white or a coralline-algae-colored purple. These epoxies are more cement-like than other adhesives and are good for creating rockwork formations but not as effective for surfaces that need a thinner, more transparent adhesive. Avoid using epoxies that aren’t designed for underwater use or with toxic materials, especially before the epoxy has fully cured.
  • Hot Glue Guns – Hot glue guns are arts-and-crafts staples but are also surprisingly effective in aquariums, most especially in freshwater tanks. For quick fixes like re-attaching an artificial plant that may have become detached from a base, they are the easiest to use and are non-toxic and ready to use soon after applying. Make sure the pieces are completely dry and clean and avoid using this glue in higher-temperature tanks.
  • Water-soluble glues – For obvious reasons, never use water-soluble glues like white craft glue in aquariums. They will never cure and will affect the water quality.




Nail polish is an easy and inexpensive solution for touch-ups and quick fixes.

  • Clear-coats – Clear-coat paints and “sealers” were some of the most popular materials in the questions we’ve received. We’ve received many questions on what kind of clear sealers an aquarists can use to cover an unsafe material and make it suitable for use in a tank. There are clear spraypaints and other paints that can be used to coat an ornament or other piece but none of these can guarantee safety. The smallest crack or opening in clearcoat can allow water in and to the surface underneath. Once the water has started to get in, it will continue to soak in and get below the clearcoat. None of these clearcoats can prevent metal from corroding or minerals from dissolving. If something isn’t safe for your tank to begin with, a clearcoat isn’t going to make it safe. Clearcoats are available in enamel or acrylic just like the paints we’ll discuss next…
  • Enamel – In my opinion, enamel paints are some of the most durable for underwater use once they are cured. Small jars can be found in many different colors in craft and hobby stores with the model-building supplies. Even most nail polishes are enamel; we’ve used nail polish to create numbered frag plugs in our retail store for years. Clear nail polish can be used for quick touchups as well. Enamel spray paints are good for quick coverage for ornaments or for backgrounds on the outside of tanks. For any form of enamel paint, make sure it is fully dried and cured before using it in your tank; “dry to the touch” does not necessarily mean it is cured. If the directions on the paint say to allow it to cure for several days, follow those instructions.
  •  Acrylic – Acrylic paint is a water-soluble paint but can be fairly water-resistant once it is cured. These paints have some mixed results among hobbyists. I prefer to keep acrylic out of the tank itself; acrylic spraypaints can be effective backgrounds on the tank but may not hold up as well in the tank and constantly underwater. The most popular of the “acrylic” paints for use in aquariums is Krylon Fusion paints. These paints are usually described as “acrylic alkyd enamels” and they share characteristics of enamels and acrylics. Many aquarists use these paints with good results, especially over plastics, but they are less effective on glass surfaces where many aquarists see the paint peeling or flaking off.



Aquarium decorations are where you can really let your creative juices start flowing! From fishing lures and hockey pucks to Eiffel Towers and zombies, we’ve gotten lots of questions about new pieces you all have been considering for your aquariums. While I obviously cant cover every single object here, here are a few of the most common materials we’ve been seeing you consider and how suitable (or otherwise) they may be for your aquarium.

    • Metal – Avoid it. Sure, you can try covering it up to protect it from the water, but as we’ve discussed, any small moisture seeping to the metal can start affecting your tank. At best, it will likely have some surface corrosion. At worst, it can leach very harmful chemicals into your water and even conduct electricity. To be safe, look elsewhere for a decoration if the object you are considering is made from or has any pieces of any type of metal.
      Coral skeletons may be fine in some tanks but can affect the water quality in others.

      Coral skeletons may be fine in some tanks but can affect the water quality in others.

    •  Natural/organic material – Use caution. This is a definite grey area. Some materials may be safe for some types of systems but others will decompose or severely affect the water quality by changing the pH or hardness. Also, where you are getting these things from can have a serious impact. Avoid using anything that you may have scavenged from nature (the beach, the forest, etc) since anything that the piece has come into contact with will go into your tank, including possibly harmful chemicals like pesticides. As a rule of thumb, it is also best to avoid putting anything natural into a very different environment than where it came from. For example, adding marine shells or corals to a freshwater tank isn’t safe and wood from the forest won’t usually hold up underwater.
    •  Rocks/Minerals – This depending entirely on what rock or mineral you are considering. Some are safe, others will affect the water quality. You can try keeping the piece you are considering in a container of your tankwater for at least a few days and monitor the water chemistry to make sure everything is remaining stable. Most rocks that affect water quality contain calcium carbonate which will dissolve at a low pH, causing the hardness to rise and pH to then increase. These rocks are usually from the ocean in origin. If you suspect this, you can try sprinkling a few drops of vinegar on your rock. If it has calcium carbonate, you’ll see it start to fizz up and dissolve. You would NOT want to addthis rock to a freshwater tank where the pH will be below around 8.0.
    •  Glass – Plain glass is fine in an aquarium. Colored glass is usually safe too, as long as it is the glass itself that is colored. The risky part comes with glass that is painted or glazed. When constantly submerged, this coloring can start coming off or be very easy to scrape off and may be harmful to the livestock at that point. Most clear-coats like we discussed above don’t bond very well with glass and may not be enough to make the piece safe for the tank. Use caution with any colored pieces and test, test, test before adding it to a tank with livestock! Most plain, clear glass is safe though and can you can make some very interesting betta bowls from fun vases and glass containers found at craft stores!
Glass is durable and lasts hundreds of years underwater so it is usually suitable as an aquarium decoration.

Glass is durable and lasts hundreds of years underwater so it is usually suitable as an aquarium decoration.

  •  Dishware and Pottery (mugs, plates, bowls, etc) – These pieces are usually safe. As a general rule of thumb, if the mog/bowl/plate/etc is dishwasher-safe, it is probably aquarium-safe. A mug with a company logo can make a great aquarium decoration in your lobby, and simple plates and bowls can make good ledges and caves (especially in a pinch). If the piece ever actually has been in a dishwasher or in dish soap, make sure it is well-rinsed and clean of any soap or food residue before adding it to an aquarium. The same rules go for pottery as well. Some unglazed pottery like terracotta pots can be safe in an aquarium and make for good breeding caves, but if they’ve housed a plant at any time, they could have absorbed fertilizers or other chemicals. If this is the case, it would be best to use a clean, new pot than repurposing one. Some decorative glazes may also not be durable enough to handle aquarium conditions. When in doubt, leave it out!
  •  Plastic and Rubber – In general, safe!! Plain colored plastics are inert and can make excellent decorations! Toys like Lego building blocks can be great, customizable centerpieces to a tank but only use

    Dishware like mugs can be excellent personal touches for most aquariums, and a good way to get your company’s logo in the tank!

    pieces free from decals and decorations that may soften and break up underwater. The same goes for hard rubber. The hockey fan in me is dying to set up a tank with a hockey puck pyramid and hockey puck archways…but again, just use plain pieces without decals or decorations.

  •  Polyresin – A number of questions that we received about possible ornaments were for figurines made from polyresin. Polyresin is, in itself, inert and safe for most tanks. The paint and embellishment used on it may not be. You can experiment with water identical to your tank conditions or try contacting the manufacturer of the piece to see if they can give you some more information. But, once again, when in doubt, leave it out!
  •  Stickers or decals – When decorating your tank, don’t be afraid to use all of the surfaces available to you! Throughout these decoartion ideas, I’ve said to avoid using anything with decals or decorations and this is true….underwater. Don’t be afraid to use vinyl cutouts, stickers, window clings or other stick-ons on the outside of the tank. You can add dimension to the decor by using the front, background or sides for images that you can’t get on the pieces inside the tank.

I hope this helps you clear up some DIY confusion and gives you some more ideas of pieces that you can (and can’t) use to decorate your aquarium. If you’ve come up with your own creative DIY aquarium ornament, we’d love to see it!


  1. avatar

    How do I deal with rust. Cause some of it is on the rim of my tank and on the screen cover.

  2. avatar

    Hello Jordan, I would recommend replacing any metal pieces and avoid these pieces when dealing with aquariums. Once the metal has begun to rust, there really is no way to stop it since the moisture will also be there with aquariums. You can use a glass or plastic lid for the tank. If the tank itself has a metal frame, I would recommend replacing it with a new and safer tank. Metal frames were used in tanks before the 80’s and have since become obsolete.

  3. avatar

    I have created five aquariums out of repurposed iMacs.

    I would like to add small logic boards and RAM chips inside as decorations, which of course contain metals.

    I tried sealing a small RAM chip with aquarium silicone, bit it was a tedious job, and I didn’t like the results (I didn’t put it in the aquarium, because it didn’t come out nice).

    Could I paint the chips and logic boards with Rustoleum Gloss Protective Enamel, or clear nail polish? – even if it took multiple coats?

    Or is there an easier way to coat the boards with the silicone seal than just smearing it on? Is there a liquid version of the silicone seal?

  4. avatar

    Hello Joel, Coating the pieces in nail polish or a clear enamel should give you more of the look you want but as I mentioned in this blog, it still won’t make the pieces completely safe for the aquariums. Tiny cracks or crazing in the enamel can allow moisture to seep in and ones it gets in, the metal will start to rust or corrode and will only get worse. I wouldn’t recommend using any pieces with metal parts inside the aquarium at all. Do you have any room between the iMac shell and the glass/acrylic that you are using as the aquarium itself? You could affix your computer parts to the outside of the aquarium but inside the case it give it the illusion of being in the water. Good luck!

  5. avatar

    To Eileen & Joel (Re: Making a circuit board aquarium safe.)
    How about embedding the circuit board in an epoxy resin block?
    Epoxy resin can be found at craft stores like Michael’s and Joann’s. It comes in several sizes. Sometimes it comes as a two part product requiring mixing. Make sure you get both parts. They’re often sold separately. Also, if the pieces are rather small, there are products such as “Ice Resin” that are used to embed small objects used in jewelry components. Some craft stores carry it, some don’t. Call around and/or buy online.
    Embedded like this, it should be air & water tight. And once cured should be non-toxic. Opinion?

  6. avatar

    Hello Pat, A resin block can be safe once fully cured and depending on the type of resin. It would give a very different look to the piece and many are not completely clear. Te safest solution is to avoid the dangerous material.

  7. avatar

    I recently used 100% clear silicone (not aquarium safe silicone) to cast some corals I had in my tank. After the silicone is removed and the original piece is taken out of the mold, will it be safe to put back into the aquarium again?

  8. avatar

    Hi Dillon, They should be safe as long as there is no uncured silicone remaining on the corals and as long as there are no added materials to the silicone you are using. Some silicones like those marketed for use in bathrooms have chemicals added to kill mold and mildew that I would be leery about adding to an aquarium but otherwise, you should be fine.

  9. avatar

    I would never thought about the nail polish – but it seams a good idea – thank you 🙂

  10. avatar

    I was wondering whether or not sculpy clay pieces would be safe to use in a freshwater tank

  11. avatar

    Hi Katie, I checked on Sculpey’s website and their FAQs page says “While our clays are non-toxic, we have not done any testing on any of the products to be used in aquariums.” Polymer clays are almost like plastic and it looks like a lot of people have used them successfully in snowglobes but it doesn’t look like many have tried using them in aquariums. I would think they’d probably be safe as long as they are fully cured and fired but you’d want to monitor their condition in the tank. The material itself is non-toxic but the durability may be questionable. The Sculpey FAQs page also has a list of their clays by durability; I would definitely go with the most durable clays over the least durable ones to be safe.

  12. avatar

    Can i use air dry clay and cover it with an epoxy paint once it has completely dried? It says it is non-toxic.

  13. avatar

    I wouldn’t recommend using air dry clay. Its difficult to tell without knowing exactly what kind of clay you are referring to, but I don’t imagine it would hold up underwater. Is it food-safe or dishwasher-safe once dried? If not, I’d avoid it…if they haven’t rated it safe for you, then its probably not going to be safe for your fish either. Coating an unsuitable material in epoxy paint doesn’t guarantee that it will be suitable afterwards or that the paint won’t craze or crack and allow water to seep in.

  14. avatar

    Does anyone know if you could put one of the garden gnome’s in a satlwater tank? What about freshwater?

  15. avatar

    Hello Marc, It would depend on what the garden gnome you are referring to is made out of, what it is painted with, etc., and I wouldn’t be able to say without knowing what garden gnome you are referring to. I would recommend reading through this blog as well as the others in this series for more information and recommendation on materials and what to look for in choosing suitable decorations.

  16. avatar

    Yes what can I use that’s safe for my fish, I just wanna glue rock and plants and not pay for expensive bottles. Does krazy glue actually work and is safe? Also what colored paints can I use to add color decor to help brighten the tank up a litte on some decor.

  17. avatar

    Would Lego’s be safe?

  18. avatar

    Hello Dakota, Any cyanoacrylate glues like Krazy Glue are safe in aquariums; it is used in aquariums quite a lot, especially in the saltwater end of the hobby with corals. Enamel paints like those mentioned in this blog would be safe for adding some color to your tank.

  19. avatar

    Hello Amanda, Lego’s are safe. I would try to avoid any with stickers or decals but the plastic block themselves are fine to use. Depending on your decoration, you may need to weigh them down since air trapped in the pieces may make them float but lots of aquarists have created some really unique tanks using Legos as decorations.

  20. avatar

    Hey can I use ceramic cups or any ceramic material for decoration in my tank? I have cichlids and I also add salt in the water.

  21. avatar

    Hello Niyant, Is the ceramic cup dishwasher-safe? As we discussed in the “Dishware and Pottery section” here and in Part 2, if it is dishwasher-safe, it is usually safe for your tank. If it isn’t, I would avoid it since it likely as a more delicate glaze that may not hold up.

  22. avatar

    I stumbled on your blog while doing some research in DIY aquarium decorations. I recently adopted the tank at my daughters school. I am trying to find inexpensive ways to create a natural setting for the fish. I really enjoyed your blog post. I was wondering if you have any thoughts on using plaster. I have seen several sources use styrofoam coated in quickcrete cement to create rock formations. I am concerned about the chemicals in the cement leaching into the tank. Would it be safer to seal the styrofoam in a layer of plaster instead? Have you any expierence with either method?
    Thanks so much!

  23. avatar

    Hi Kate, thanks for commenting. We would hesitate to use plaster or any material that is not specifically designed for aquariums. The reason would be that anything not made for an aquarium could include chemicals or materials that could affect your water quality or the health of your fish. In our opinion it is not worth the risk. Thanks!

  24. avatar

    Are vinyl toys safe for aquariums? If not, can you cover it with a coat?

  25. avatar

    Hello Nicole, The vinyl itself would likely be fine but any decals on it wouldn’t likely hold up. You could try using a clear enamel paint but anytime you coat something that isn’t safe, there is a chance that any tiny cracks in the coat are going to allow moisture to seep in to the toy.

  26. avatar

    Hi. Can i use cotton?

  27. avatar

    Hello Tahsina, I wouldn’t recommend using anything organic like cotton since it will start to break down and decompose, particularly in certain water conditions like saltwater or low pH.

  28. avatar

    Thanks eileen

  29. avatar

    Hi I am making my own 3d background out of polysterine and will be silicone to the back to the tank. I am currently sculpting small pieces of polysterine to make a feature wall and wonder do i have to use the aquarium silicone to stick on as only comes in large bulky tube I need something smaller and winder if there is a glue for polysterine. The end result will be covered in 3 layers of quick Crete and painted as well but need something safe on polysterine
    thanks jo

  30. avatar

    You can use many things to glue the foam together. Spray Foam works, Gorilla Glue works, Hot glue works, there are also “foam glues” that are available that work, you can get at hobby shops. Just test on a small piece of scrap first to make sure there are no odd reactions. For that log I built in the cylinder , I used toothpicks to hold the pieces where I wanted them, and used small amounts of sprayfoam to glue them together and fill any voids, then shaped the foam after it cured, and coated with Drylock. The quick crete will work also, just need to be careful of pH issues using concrete products. Foam Glue Google Search

  31. avatar

    Hey thanks alot for that appreciate it heaps .I have spent days sculpting the foam and don’t want to wreck it all with the wrong stuff

  32. avatar
    Brianna Cavanagh

    I was wondering if you could help me out. I’m trying to figure out how I could make a cave or tunnel thing out of rocks from outside but i don’t know what to coat them with to see if they’re safe… Can you help me?

  33. avatar

    Hello Brianna, Using anything from the outdoors in your tank is very risky and I wouldn’t recommend it at all. It is impossible to tell if they may have been exposed to any chemicals like pesticides and the composition of some rocks like limestone can change your water quality. It would be much safer to use base rock from an aquarium supplier in your tank and choose the type of rock carefully to be sure you aren’t using any that can affect the water in a way that will harm whatever types of fish you have/

  34. avatar
    given management

    There’s definately a great deal to learn about this subject.
    I really like all of the points you’ve made.

  35. avatar

    I want to build something with Legos for my aquarium. I keep reading people say that air will get trapped inside the Legos? Is that a problem? Will I need to super glue each piece together to be successful? What to you recommend to keep the final product from floating?

  36. avatar

    Hello Courtney, Usually, the Legos don’t snap together tightly enough to trap air. You can try rotating your piece around underwater as you submerge it to give the air a chance to escape. Putting it in the tank straight down will make it much more likely for the air to get trapped since it will rise to the top of each piece. If you have any fish that are large enough to eat the Lego pieces in your sculpture or any of the pieces fit together loosely, I would recommend gluing it together to make it more secure. Otherwise, it will likely be solid enough without gluing. If you find the piece is floating, you can make a base for it out of one of those big, flat Lego base pieces and bury this part in the substrate. Some Lego pieces are also big enough to put small fishing weights into the pieces as you put them together.

  37. avatar

    Hey I had 4 now I have just one chilid left in my tank should I purchase more or is it fine to keep just one.(as I am not very keen to buy more)
    And can you also suggest me in how many days should I clean my tank completely.
    And what all precautions should I take.

  38. avatar

    Hello Niyant, I would recommend calling and speaking with someone in our Fish Room at 717-299-5691 about your tank and situation. Some cichlids are fine alone while others are better in groups so I can’t answer that without knowing what kind of cichlid you have. It should never be necessary to clean a tank by completely emptying it; this would start the tank over new and it would have to go through its cycling process again. Without knowing more about your tank (size, what kind of fish, water parameters like pH, Ammonia, Nitrite, Nitrate, hardness, temperature) and what you are taking precautions against (poor water quality, disease, etc), I can’t give you any more specific recommendations. If you are looking for information on basic aquarium care and maintenance, you can also view a lot of different articles on different topics in our Aquatic Article Archive.

  39. avatar

    I”m building a castle with Sculpey clay – I’d like to add some additional color to some items like a red or copper parapet — If i paint the clay white after baking with enamel paint – does the enamel need to be sealed with any type of sealer or finish? Or should i just use the colored clay? (which ofc means another trip to Joann’s crafts lol

    I plan to let this ‘gas out’ from any silicones or glue fumes for a week at least, and probably submerge it into water without fish for a week to be on safe side and check chemical levels to make sure nothing in water changes
    this small castle will go in a 10 gallon tank which houses guppies atm, and once i move guppies in a few weeks to my 55 gallon i plan on putting a butterfly betta male in this tank.

    if this is a success i want to do a larger castle for the 55 tank
    and maybe a ship or something in my hubby’s 100 gallon saltwater tank
    any advice or hints would be great

    thanks for the great articles

  40. avatar

    Hi Leslie, I’m glad you enjoy our blogs. Enamel wouldn’t need sealed once it is fully dried and cured. We’ve used enamel paints quite often in our Fish Room and as long as they are allowed to fully dry, they have held up well for the most part. Sculpey isn’t proven to be aquarium-safe. Another commenter asked about them back in May; I would recommend checking out the link in that reply for Sculpey’s website and clay durability information.

  41. avatar

    I’ve read a bunch of tank forums the last week (when i shoulda been out running or working hahah) and so far a majority of them have used the sculpey with great success to make caves and such (but i’m a castle freak so … haha)
    – so i’m gonna give it a try and may add some enamel paints for more colors than what i have 🙂 thank you for your reply

  42. avatar

    I just bought a 55 gallon fish tank and I want to put a fake skeleton in it but the only ones I could find assembled were plastic and contained metal

  43. avatar

    Hi Savannah, I do not recommend putting anything metal in the tank, coated or not. Any moisture that gets through that coating through small pores or cracks can reach the metal and cause corrotion and other issues. Plastic pieces, glass or pottery without delicate decorative glazes should be safe. I would keep looking or disassemble the skeleton and remove the metal. With Halloween coming up, try checking for plastic Halloween decorations or party favors.

  44. avatar

    Hello, what is the best way to adhere a paper image to show through the back of a tank?

  45. avatar

    Ho Abbey, That depends on the type of paper. In the examples I did in the second part of this series, “Aquarium Decoration Ideas – Fish Bowl Designs & DIY” as well as one of my tanks at home, I just used transparent tape on the edges since they were hidden by the frame and corners. You could also use a spray adhesive if the paper is laminated.

  46. avatar

    Hi Eileen,
    Thanks for this wonderful post and responses. Wondering if you know if metallic spray paints would be safe to use as I want to do a design with copper colored pieces. Also if you know anything about coating objects with polygen which I just heard on the show “Tanked” – they were coating sports equipment to put in an aquarium and I can’t find anything on Google. Thanks!

  47. avatar

    Would it be safe to make an aquarium cave out of porcelain, and then glaze it in food-safe glaze??

    Thank you

  48. avatar

    Hi Shannon, Glad you are enjoying this blog series! In my experience, paints with special finishes like metallics and neons don’t tend to hold up as well underwater but it depends on the type of aquarium and water conditions (lighting and water chemistry will affect the colors differently). I would recommend using an enamel paint like those used for models rather than a spray paint…they tend to hold up better when we’ve used them here. I would also be sure to coat the finished pieces in a clear enamel as well to help protect it. From what I have been able to find online, the product referred to on that show was Polygem. From their website, it appears to be a clear epoxy coating which is usually safe when used correctly. I’m not familiar with that product specifically and still wouldn’t recommend using unsafe materials in an aquarium – coated or not – but I do know that the artificial pieces in many large public aquariums are epoxy-based or -coated.

  49. avatar

    Hi Dante, Yes, that should be safe. Once again, if it is a dishwasher-safe or food-safe glaze, it is probably safe for the conditions of an aquarium. Porcelain and other ceramics like mugs, plates and bowls are generally safe to use as aquarium decor.

  50. avatar

    Great post! Thank you!

    I want to design an interactive toy or two for my boyfriend’s green spotted puffer. The poor thing is so bloody bored! I looked everywhere, but I found no pre-made toys and everyone seems to be of the ‘they’re-fish-not-dogs’ mentality. But I could totally see our puff rolling a ball along a track or pushing through door flaps or whatever. I found your blog post as I was hunting for tips on materials to use, since I will obviously need to make these things myself. If you have any other ideas for things I could use or try making, I’d love to hear them!

  51. avatar

    Hi JD, I’m afraid that puffers won’t really “play with toys” like you might want to see. You can look for small plastic toys like these cat balls (but without the metal bells) or other similar small animals or even baby toys without paint, stickers or decals and put fresh, freeze-dried or (thawed) frozen food in the center for them to feed on. You can also add occasional live feeders like Ghost Shrimp to help them use their natural hunting instincts.

  52. avatar

    What a great resource this blog is. I want to use a bust from Restoration Hardware in a tank, they are made from resin which I am sure is safe, the problem is they are “hand finished” presumably with some sort of paint which makes it hard to know if it would be safe. Do you have any thoughts?

  53. avatar

    Thanks, Ron! Polyresins in themselves are usually safe but you are correct in that the paint used on them may not be. I would recommend soaking the bust in water with similar conditions to your tank for a couple weeks to make sure it holds up. You can use clear enamel topcoats or spray paints to help safeguard it but, as always, they shouldnt be used to make a potentially dangerous and unsafe material “aquarium friendly”. It is always a bit of a risk using something with unknown materials. You can try asking the store or manufacturer what kind of paints they used.

  54. avatar

    I’m trying to make magnets aquarium (fresh water) safe. I plan on using them to keep power heads in place instead of the suction cups, which always seem to come loose. The magnets are the strong neo-something type. What can I cover them with to make them usable in the tanks?

  55. avatar

    Hello Dominick, High-quality neodymium magnets are usually safe and don’t rust as easily as iron-based magnets but it is still not a good idea to use them in water constantly. Epoxy-coatings will help them last longer but any small scratches or cracks in the coating will still let water in. Keep in mind that the magnets can affect the mechanics of the power head, especially the impeller that spins inside the powerhead. VorTech Quiet Drive circulation pumps use magnets in the same way to hold them onto the side of the tank and the magnet can only be attached or adjusted when the pump is off due to the interference with the propeller. You may want to contact the manufacturer of your specific powerhead to discuss how magnets may affect that piece specifically.

  56. avatar

    I see several times to avoid metals. but I’m dying to make a tank out of an old drum (instrument) that has a clear front but everything else is metal. it’s a whole lot of hardware and a metal frame. is this a realistic possibility at all? if I seal it with something and then create an acrylic tank for the inside would it still be unsafe? people make the coolest diy tanks and this would be awesome looking, but I don’t even know where to start. thanks for any help you can give.

  57. avatar

    Hi Mary, I would recommend having a tank custom-built to fit inside of the drum if you would like to use it as the shape and “frame”. Most of the specialty tanks you see that that inside of unconventional items have had tanks built to fit into them and give the illusion that the phonebooth/toilet/blender/computer/tv/whatever actually IS the tank. A web search for “custom acrylic aquariums” will bring up a number of companies that specialize in creating aquariums like this and may be able to give you some design advice and quotes.

  58. avatar

    I am having a hard time finding seasonal ornaments for my aquarium. What can I use to sculpt custom made ornaments and seal them that will be durable and safe for underwater?

  59. avatar

    Hello Cheryl, I would recommend taking a look through all three parts of this blog for some ideas on materials and pieces you can use. Dishwasher-safe ceramicware and glassware and plastics like Legos can be used as well as fully-cured enamel paints. You can also use decorations like backgrounds or static-cling decorations on the outside of the glass. We also offer Disney Frozen decorations which include an ice castle and Olaf the Snowman. Some aquarists have used clays like Sculpey but their safety is questionable; the Sculpey brand will not endorse that product for aquariums.

    From a previous comment reply in May 2015:
    I checked on Sculpey’s website and their FAQs page says “While our clays are non-toxic, we have not done any testing on any of the products to be used in aquariums.” Polymer clays are almost like plastic and it looks like a lot of people have used them successfully in snowglobes but it doesn’t look like many have tried using them in aquariums. I would think they’d probably be safe as long as they are fully cured and fired but you’d want to monitor their condition in the tank. The material itself is non-toxic but the durability may be questionable. The Sculpey FAQs page also has a list of their clays by durability; I would definitely go with the most durable clays over the least durable ones to be safe.”

  60. avatar

    Hi I’m wanting to put some decorative dried twigs inside my fish tank they are already dried out is this safe to do? I went ahead and started soaking them they have been sitting in a tall vase for about 4 years beside my fireplace I thought I’d use them to change the landscape of my tank is this a good idea? Thx☺☺

  61. avatar

    Hello Janice, I wouldn’t recommend adding any decorative wood that is not specifically sold for aquariums to an aquarium. It is impossible to tell what it may have been treated with or exposed to and many woods will decompose and affect water quality much faster than the driftwoods sold for aquariums. All woods, including aquarium-safe driftwoods – will affect water parameters over time so it is important to consider what type of fish you have and the water parameters they need as well.

  62. avatar

    I want to actually sculpt my own orniments with Sculpty brand clay to make a tea themed tank. Since I have to glaze the clay anyway, what brand and type of glaze You would advise me to use for oven cured clay?

  63. avatar

    Hello Heather, I would recommend contacting Sculpey about what glazes are best to use with their products since not all glazes can be used with all clays. Past commenters on this and other blogs in this series have asked about Sculpeys clays and they don’t guarantee that any of their clays are aquarium-safe. That said, enamels are usually safe when fully cured and any dishwasher-safe dishware or ceramics are usually aquarium-safe.

  64. avatar

    Pop(plaster of Paris) ornaments are good for fish tank and fishes or not…

  65. avatar

    Hello Sourav, Plaster of Paris is not safe in aquariums. It has a carbonate base and will dissolve over time and will affect the water chemistry.

  66. avatar

    I made an Asian style clay water fall (air dry clay) painted it with acrylic paint and coated in polymer resin. Can I use anything ells to coat it and make it safe?

  67. avatar

    Hello Amanda, Air-dry clay is generally not safe in aquariums and will not hold up over time. I do not recommend using unsafe materials, even coated in paints or resins, since any moisture that reaches the material through cracks or holes will affect it.

  68. avatar

    How would you go about making a cave out of sealant and aquarium gravel? Like to shape it around or over something like a mold. Maybe cover the item with wax paper then start to build around it and then remove the mold and wax paper when the sealant is cured?

  69. avatar

    Hi Chelsea, There are a number of ways to create the cave, depending on the look you want, the materials you are using and the function for it (as cover for larger fish, decorative and with smaller fish, etc.). The way you mentioned is one way to do it but might have some structural issues in staying up without collapsing , depending on the type of gravel. If you are using larger pieces, you can try piecing it together and building it up; think igloo for smaller rocks or Flintstone house for larger, flat pieces.

    For a cave or tunnel with some more structural strength, you can try covering an aquarium-safe base with your gravel or rocks. PVC tubes or terracotta pots make good bases to build on; you can either leave them intact and lay it on its side or you can cut it in half to make an arc (from the tube) or a cave (from the pot). For a structure like this, you can use the silicone as glue to stick each piece on for larger pebbles, or you can cover the piece (or patches of it) in the silicone and either roll it in your gravel or gently press handfuls of your gravel into the silicone.

    Some DIY Tutorials for projects like this are on our list of projects-coming-soon, but until then, a Google search for “DIY aquarium cave” will bring up some examples that have used some techniques similar to these.

  70. avatar

    I’ve had the worst luck with clearomizers. Basically the metal threaded cap that’s attached to the plastic tank has started leaking to some extent. This is the third one. I generally tend to save crap so I tossed em in a box. So my question is, can I use 100% waterproof silicon and run a circle of it on the outside of the tank where it connects at to stop the leaking?

  71. avatar

    What clay like product can I use to sculpt with and what should I coat it in

  72. avatar

    Hello Edward, We don’t deal with clearomizers in the aquarium trade. I would recommend contacting the manufacturer of that product or a dealer that handles those specifically.

  73. avatar

    Hello Amanda, I would recommend reading through the three parts of this blog series for ideas. Fired pottery without decorative glazes are generally safe, as are product considered Dishwasher Safe and Food Safe.

  74. avatar

    I’m working on a kitchen theemed tank, but the only decent looking model furniture I can find for it is made of wood. Plastic furniture is always in weird colours so I’m not sure I’d like to use it. Is there any way to make wooden toy furniture safe for tank use? Any sort of sealant?

  75. avatar

    Hello Chesh, I do not recommend using unsafe materials, even coated in paints or resins, since any moisture that reaches the material through cracks or holes will affect it. It is also difficult to tell with that type of furniture if it has been treated or painted with paints, dyes or glues that wouldn’t hold up underwater. Try looking for ceramic or glass pieces. I did a quick search for “ceramic dollhouse furniture” and it is certainly out there online…just make sure that any pieces you find are fired and that the decoration is permanent. The seller should be able to provide you with information on the materials and durability.

  76. avatar

    I was wondering if I could use a glazed ceramic cup

  77. avatar

    Hello Bswarth, Is the ceramic cup dishwasher-safe? As we discussed in the “Dishware and Pottery section” here and in Part 2, if it is dishwasher-safe, it is usually safe for your tank. If it isn’t, I would avoid it since it likely as a more delicate glaze that may not hold up.

  78. avatar

    Hi Eileen, I would like to put about 30 pounds of limestone in a 108 gallon planted tank. As I am sure you know, this is sure to raise the pH. What would be the best way to seal these rocks to avoid this. Thank you, Joe

  79. avatar

    Hi Joe, I wouldn’t add limestone to that tank. It would be much safer to add an inert rock that isn’t going to affect your water chemistry. I do not recommend using unsafe materials, even coated in paints or resins, since any moisture that reaches the material through cracks or holes will affect it.

  80. avatar
    William Franklin (U.K.)

    Wow! I finally got here. That is a great post and there is much to be learnt from the comments. Eileen you truly know your stuff. I have a question. I have a 200L (52 gallon?) planted fresh water tank with around 80 fish, the largest being 2 clown loach. When planting new cuttings and bunched plants could I use paper to help secure them under the substrate (provided its unbleached of course) as l my 2 loach have a habit of digging out any thing new I plant.

  81. avatar

    Hi William, Thank you, glad you enjoyed this post! I haven’t had any experience using paper under the substrate and cant seem to find any other experiences with it. I don’t think that the paper or paper towels would do any harm themselves but I would be a bit concerned with it trapping debris underneath and not allowing gases to diffuse safely. That could lead to some water chemistry issues as it builds up that would be very dangerous to your fish and plants. Loaches will dig…that’s just what they do…and a 200L tank is pretty small for them especially as they approach full grown (and without knowing what the other fish are, 80 fish total for that size tank is pretty crowded). Rather than the paper, I might try planting the plants through some netting. You could sacrifice a net and cut the mesh out of it or use pond surface netting and cut an X or a hole in it to put the plants through, then cover the top of the netting with substrate; just be sure that the size of the hole is adjusted as the plants grow. I wouldn’t cover the entire tank with the netting, but maybe just about a 6-inch diameter so around the base of each plant.

  82. avatar
    William Franklin (U.K.)

    Thank you for the advice. I wasn’t too sure so I thought I would ask someone of better experience. I wouldn’t worry about my clown loach, all my other fish are nothing more than tetra’s. While they cluster to the middle and top the 2 loach (fully grown – 6 years old) have the run of the bottom of the tank. With the tank being 5ft long by 2ft high there is around 2-3 inches between fish at all times. Just as a final side note, I do give my loach cucumber weekly and it does seem to curb their digging nature but you quickly find out when they have eaten it all.

  83. avatar
    William Franklin (U.K.)

    And I like the idea of the netting but is there something which is natural and would slowly degrade and add to the ecology of the tank?

  84. avatar

    Hi William, I’m not familiar with any materials like that that would be safe in aquariums and not affect the water quality. I’d recommend trying the forums on a planted aquarium site to see if other hobbyists have tried anything similar. Since I see you are in the UK and your availability may be different than what we have here in the US, a site like the UK Aquatic Plant Society might be a good place to start.

  85. avatar


    I’ve built a Styrofoam background for my 75g tank. I used sanded grout instead of cement because of the color pallet available. Grout has roughly the same characteristics as cement but was wondering if I should seal it before adding it to the tank. Any advice would be helpful. Thanks.

  86. avatar

    Hello Len, I spoke with another biologist here who has more experience using grout and cement in tank backgrounds. With any cements and grouts, you will run the risk of the material leaching into the water and affecting the water chemistry by buffering the hardness and raising the pH very high. He recommends that you soak the background in water and monitor the pH during that time to see any effect that the background has on it. If it does affect the pH, you will need to continue soaking the background and changing the water often until all of that material is leached out and the pH stabilizes which could take several weeks to a few months. If this tank is saltwater or hard/high pH freshwater (like an African cichlid tank), these effects might not be as critical. If this is for a soft water or lower pH freshwater tank, it may be nearly impossible to get this into a safe hardness and pH range for those fish and you may be better off starting over with a more pH-friendly material like DryLok, a latex-based waterproof concrete that can be tinted with concrete stains or latex hobby paint. We have a large goldfish display tank here with a stump centerpiece that was created using this method. Any cements or grouts are virtually impossible to seal otherwise.

  87. avatar

    Hi I want to paint some glow in the dark powder onto some plastic inflatables any recommendations on a waterproof flexible clear coat to use to mix glow powder with? This is for a big nighttime outdoor glow in the dark underwater fish exhibit with floating inflatables of whales, sharks, sea turtles, ect. which will be displayed in a salt water bay which is connected to the ocean where people can kayak and paddle board and boat around at night with glowing sea creatures. So we need durable flexible water proof non toxic clear coat we can mix with the glow powder to put on these big inflatable fish so they glow.

  88. avatar

    Hello Sandy, I’m not familiar with any products that we’ve used that would still be flexible for that application. Latex paints might work if you can find a clear latex but I’m not sure how that would work with the powder you mention. Since it sounds like you are using these “in the wild” as opposed to an aquarium like we discuss on this blog, you would also want to make certain everything you use is environmentally-friendly as well. I would recommend contacting a paint company like Krylon to see what they would recommend for that use.

  89. avatar

    I bought a new ceramic pot you can put flower in. it looks like the glaze is baked on. can it go into a fresh water aquarium?

  90. avatar

    Hello Nancy, Some decorative glazes are not durable enough to hold up in an aquarium. If the pot is dishwasher-safe, it is probably aquarium safe. To check its durability, you can soak it in water similar to your aquarium conditions for a length of time and test for any changes in pH or water hardness or in the condition of the pot and glaze.

  91. avatar

    Do you have any suggestions on what I could use to weigh down legos in a tank? I was thinking of filling them with aquarium safe silicone, but I’m not sure. I just want to drop a bunch in like aquarium rocks. I don’t want to build them in there.

  92. avatar

    Hi Danielle, Have you tried dropping them in to see if they sink on their own (making sure there are not bubbles trapped underneath, of course)? The silicone could work as long as you let it cure fully. Depending on the size of the pieces, you could also try gluing small pieces of gravel inside of them…any cyanoacrylate glue like Krazy Glue would work for that.

  93. avatar

    Hi everyone!!!! I am so glad I found you guys cause I have a ton of questions. Ever since I got hooked on “TANKED” I have been fascinated by the way they incorporate figures inside the rich tank as props. Now, I would really love a full blown explanation on a couple of things, if you may be so kind….The first is, I would like to place inside a 75 gallon tank KISS figurines, but I need to know if I spray the figurine with clear coat enamel:
    A.) which is the BEST kind of clear coat enamel and should it be sprayed, hand brushed, and how long does it need to “cure”;
    B.) If the figure is completely made of plastic, is the enamel enough and how many coats?
    C.) if the figure itself is plastic but the clothing is made of fabric, do I need to spray the clothing with soething other than enamel (I ask, because on an episode of TANKED, they covered Jeff Dunhams figurines with resin which made the material hard, and I am aware that they did this to clog up the pores and then use it as a mold) but would this same principle be applied (the clogging of pores on the clothing material) as to then seal with enamel?
    D.) Assuming that all these details have worked and the figurines are in the fish tank, would I need to eventually re-spray the dolls/fighurines
    E.) on another note, I have used Thompsons Water Seal on wood to protect it from water, could I use Thompsons water seal instead of enamel or as a primer before using enamel to ensure the seal.
    I really hope you can help me out here cause if I can make that fish tank look the way I’m imagining it will, its gonna look killer and I promise to post the pictures 🙂

  94. avatar

    Hi Arnold, I’ll do my best to cover all of your questions for you…
    A) The “best” is a matter of personal preference and the time to cure would depend on the brand, the thickness of your coat, temperature and humidity in your area and other factors. Definitely follow the manufacturers’ directions and allow the piece to cure for AT LEAST as long as they recommend, if not longer. We’ve used Krylon products here with good success (especially for larger areas) but clear model enamel or nail polish works as well for small touch-ups. I prefer several light coats of spray personally rather than hand-brushing that can leave small pores or bubbles. Whatever method you use, I recommend doing multiple layers and avoid very heavy layers to get the best coverage and even curing.

    B)The enamel is usually plenty. If it is plastic and only plastic, even the enamel may not be 100% necessary but if the plastic has any kind of decals or coloring, the enamle will help protect it. As I already mentioned in (A), several light coats will protect better than one thick one.

    C)I don’t recommend using fabric at all, coated or not. It won’t hold up as well and gives a good foothold for algae and other debris to cling to. I don’t watch or agree with many of the things that are done on Tanked so I can’t speak to what they did on that show.

    D)Possibly. It depends on the material and water conditions. If the tank reaches any extremes in pH, temperature, Ammonia or has fish that nibble at the decorations, they may need touchups. Also, lighting may affect the colors. Keep an eye on everything you put in and make it a part of your regular maintenance to check the durability of the pieces.

    E)That would be a better question for Thompsons directly. Sealants like that may have chemicals that can leach into the water and affect the chemistry and health of the tank. My general rule-of-thumb is that if it is safe for potable use (to drink or eat off of) or dishwasher-safe (for durability), it is probably aquarium safe. If you wouldn’t coat your coffee cup in Thompsons Water Seal to drink out of, don’t make your fish do the same.

    Hope that helps. Good luck!

  95. avatar

    Eileen, your help has been amazing and you’ve made my day 🙂 I thank you so much for all of your help.
    It will take me some time, but I promise to send you pictures of my project.

    Thanks and take care!

  96. avatar

    You’re welcome, Arnold. Have fun with it!!

  97. avatar

    Do you know of any 3d printer materials that are aquarium safe?

    I’m looking to do an astronaut helmet for my Dr. Who tank, but can’t find one anywhere that’s aquarium safe.

  98. avatar

    Hello Yenni, Going for The Impossible Astronaut look? Great episode. As for the materials…that is difficult to answer without knowing what specific materials the printer is using. Not all 3D printers use the same material. Depending on the scale you are going for, you could try using Lego figurines (tons of astronauts there), or you could create your own with a glass or plastic globe (fish bowls, light fixtures, planters…check your local craft or hardware stores) and aquarium-safe paints like enamel. River’s helmet wasn’t too complex…white paint for the helmet and smokey silver-grey paint for the visor.

  99. avatar

    If I wanted to build my own small “swamp home” for my aquarium, what type of wood is my best bet to be used for build to make it aquarium safe?
    Trying to make a bayou themed aquarium.

  100. avatar

    Hello Chase, Are you creating a freshwater or saltwater aquarium? What pH and water hardness are you trying to maintain? What types of fish and other livestock are you looking to keep? Any type of wood will affect the water conditions over time and are not suitable for all types of aquariums. African Mopani wood is the most common kind of “driftwood” available for aquariums or you can look for artificial ornaments like these by Design Elements and Exotic Environments. Check around some reptile supplies as well; a background like this mangrove background may help with the look you are going for.

  101. avatar

    It’s for a crawfish tank that has ghost shrimp, tetras and snails. Crawfish is the main focus everyone else is there will probably turn into a snack at some point. But what I meant by wood is wood to actually
    Build a small house. Thanks for the reply!

  102. avatar

    You’re welcome, Chase. Mopani should be fine in a crawfish aquarium and you may be able to find some that you can cut apart to build your house. You could also try stones like petrified wood or slate. Have fun building!

  103. avatar
    Daniel Kleinrok

    Hi Eileen please help if possible, I have 50+ lbs seiryu stone I’m trying to put in my tank. I used a grinder and flattened as much of the “bottom” of the stone as I could. But its still top heavy. I want to use an epoxy. I’m very familiar with commercial injection resins. So my question is what is in epoxies that would make them unsafe, and I have an epoxy called SPLASH ZONE, by Pettit. Its an underwater marine epoxy used in commercial construction. Have you ever heard of it being used in an aquarium does it work.
    Thank you.

  104. avatar

    Hello Daniel, I’m not familiar with that product. Your best bet would be to contact the manufacturer of it directly for their suitability. A marine epoxy should be safe underwater but given the confined conditions of an aquarium, there may be complications. I see on the website for that product that it does say it is “not for use in potable water”. Given that restriction, I would be extremely hesitant to use it in an aquarium.

  105. avatar
    Daniel Kleinrok

    Thank you, I noticed you recommended Drylok concrete. Wasvthat the Drylok concrete patch? Could I use that to buildup the bottom of this stone to create a foundation?

  106. avatar

    Hello Daniel, You could use Drylok to build up a base, just be certain that it is fully cured before going into the aquarium. Concrete like that can also effect water chemistry so depending on what parameters you are trying to stay within – especially for pH and hardness – you may have some issues with using a concrete.

  107. avatar
    Erica Gattiker

    Hi! If this is still active and it’s not too much trouble, I have a question.
    I’m trying to make a Spock, Kirk, and McCoy set to put in my aquarium. I’m trying to find relatively inexpensive way to make them explore my freshwater ‘world’. I’m having trouble finding legos to use, so I’m thinking maybe doing clothespin dolls, and wrapping them with embroidery thread, then sealing them with clear nail polish or enamel or superglue or something. Do you think this might work, or should I keep looking?

  108. avatar

    Hi Erica, Sounds like a fun tank! I would stay away from embroidery thread…fabrics like that usually don’t hold up too well underwater and those surfaces are hard to clean and make good algae-growing surfaces. If you want Lego figures, try looking online. I found Star Trek men on Minifigures.com, CustomBricks and a few other sites on a quick search. Some action figures are safe as well; just look for ones without metal parts in the joints. I found action figures listed on Walmart.com and Amazon as well. Good luck!

  109. avatar
    Erica Gattiker

    Thanks for the advice. I’ll definitely check out the Lego link. I’ve been having trouble finding action figures and such that are under $20, for some reason.

  110. avatar

    I have some small glazed ceramic pieces, would those be okay to but in my beta fish’s bowl?

  111. avatar

    Hello Brit, It would depend on the durability of the glaze used. If it is a food-safe or dishwasher-safe glaze (inside and out), it is likely safe for your aquarium. If it is a more delicate decorative glaze, likely not.

  112. avatar

    Glofish have GloFish Create Your Own Aquarium Background, but I can’t find it anywhere! It’s a black background that you draw on with markers. You can erase it and draw a new background. I was wondering what type of markers they would be using and what type of black background?

  113. avatar

    Hi Crystal, That isn’t a product that we sell so I don’t have any information on it. I would recommend visiting the GloFish website (www.GloFish.com) and contacting them with you question. It would have to be some kind of fluorescent ink to glow under the lights but I don’t know what type of ink base they are using to be erasable. You could try experimenting with some type of laminated material and markers or paints.

  114. avatar

    Hi I wish to create my own statue for a friends fish tank as he wants something specific but can’t find it online I was wondering if I was to make it myself from clay and fire it will it be fine for his fish tank ?

  115. avatar

    Hi Karlee,

    Thanks for commenting. We would probably caution against using that…it would be hard to know if any chemicals or properties in the clay would be a problem for your aquarium inhabitants. Sorry thats not a definitive answer, but it’s probably better to be safe than sorry! Thanks!

  116. avatar

    I found this article in a google search on “fish safe decorations”, I know it is from 2014 but it looks like people are still replying to it in 2016. so I have a question!
    Cement? Just plain cement. Except, molded into shapes. Not necessarily painted. And then let cure for whatever the recommended time is (I haven’t read on the bag)

  117. avatar

    Hi Kayla, We have answers! ….kind of. Cement can be tricky. With any cements and grouts, you will run the risk of the material leaching into the water and affecting the water chemistry by buffering the hardness and raising the pH very high. You would need to soak the piece in water and monitor the pH during that time to see any effect that the piece has on it. If it does affect the pH, you will need to continue soaking the piece and changing the water often until all of that material is leached out and the pH stabilizes which could take several weeks to a few months. If this tank is saltwater or hard/high pH freshwater (like an African cichlid tank), these effects might not be as critical. If this is for a soft water or lower pH freshwater tank, it may be nearly impossible to get this into a safe hardness and pH range for those fish and you may be better off starting over with a more pH-friendly material like DryLok, a latex-based waterproof concrete that can be tinted with concrete stains or latex hobby paint. We have a large goldfish display tank here with a stump centerpiece that was created using this method. Any cements or grouts are virtually impossible to seal otherwise.

  118. avatar

    Hi I’ve used a fabric liner on a rock to put a message on. Can i use it as a decoration in my tank or will it kill my fish?

  119. avatar

    Hello Munz, I’m not sure what you are referring to as a “fabric liner”. Did you attach fabric to a rock, or is this a type of paint or glue that you used?

  120. avatar

    Hi, can anybody give me a firm answer on which paints i can use in my new freshwater aquarium for ornament decoration, i keep seeing use non toxic fish safe but no-one specifies a manufacturer or brand!
    PS i’m in the UK.

    any help would be appreciated.

  121. avatar

    Hello slinky, We are located in the United States and I don’t have any information on brands available in the UK. You can use the guidelines in the Paint section of this blog as well as in Part 2 of this blog series to help you with shopping for suitable paints in your area.

  122. avatar

    Hi! I really loved your blog! I just got a new Betta girl and was hoping to put some Halloween decorations from michaels in her tank. Any suggestions?

  123. avatar

    Hi Claire, Glad you are enjoying it! Michaels has some great decorations but definitely make sure to avoid anything with glitter and rinse off anything you do try very, very well to get rid of anything that might be sticking to it (I know how fond they are of putting glitter on everything!). Glassware and anything food-safe or dishwasher-safe should be good. Most plastics should be OK as long as any decoration isn’t a sticker. Be careful with other ceramics since decorative glazes may not be strong enough to hold up underwater and definitely avoid any florals (artificial or otherwise) and feathers. Have fun!

  124. avatar

    Hi I was wanting to make buildings and possibly put some kind of underwater lights in them. I would like to know what you recommend to make the buildings out of. Do you have a list of safe materials we could consider to use and any recommendations on lights? I was thinking the cement stuff would be to heavy for what I’m wanting to build thanks in advance.

  125. avatar

    Hello Anonymous, Underwater LED lighting would be the safest choice. There are a number of underwater lighting options available. Most are for ponds but products like this one for aquariums specifically are also available. I wouldn’t be able to provide a complete list of materials suitable for underwater use beyond what we discussed in all three parts of this blog.

  126. avatar

    What would you recommend for painting a **LIVE** fresh water clam shell ?

    I want to paint gold with plastic gems and small pearl beads {the arts & crafts string pearl beads}

    they are golden clams the reason i want to paint gold with pearls and gems XD

  127. avatar

    Hello Jennifer, I wouldn’t recommend decorating a live animal. Aside from the physical effects on its shell, the added weight and change to its shape will affect how well it can move.

  128. avatar

    I want to use some kind of string to anchor a floating decoration. What kind of string is safe to use in my aquarium?

  129. avatar

    Hello Sue, Fishing line would be a good choice for that type of use.

  130. avatar

    What is the best way to make outdoor rocks safe for an aquarium

  131. avatar

    Hi Joe, That would depend on the type of rock. I generally don’t recommend adding most rocks taken from the “wild” to your aquarium since it is impossible to tell what they may have been exposed to over time that might leach into your aquarium. Also, some types of rocks and minerals will affect water chemistry by raising or lowering pH or water hardness.

  132. avatar

    I am building a 500 gallon bait tank out of a galvanized metal tank it needs to be painted I plan on sending it I am just wondering if powder coat is a good option that will not kill my fish

  133. avatar


    i have converted and old indoor hot tub into a pond but it is white and want to coat the inside with a colored rubber or even a pebble apoxy but of course want to be sure it is fish safe and hold up under water.


  134. avatar

    Hello Tracy, Maritime paints are usually safe as long as they don’t contain any extra chemicals like algacides as are many epoxies. Looking for paints that are rated as safe for potable water is usually your best bet and contacting the paint manufacturer would be the best way to check if it is safe. Most won’t be able to tell you if it is fish safe, but if it is safe for potable (drinking) water, it should be fish-safe. Using a recycled hot tub or swimming pool is always enormously risky even if repainting or coating because of chemicals that may have been used in it over time.

  135. avatar

    Hello Ben, Metal is always very risky to use as a fish tank or pond. Even if coated, galvanized metal can rust over time. It may last longer than other types of metal, but it can still rust depending on the composition and even the smallest cracks in the coating can lead to leaching down to the metal and back into the tank. In general, for any paints and coatings used for fish tanks, your best bet would be to contact the manufacturer about its safety. Most won’t be able to tell you if it is fish safe, but if it is safe for potable (drinking) water, it should be fish-safe.

  136. avatar

    How do I make a pair of sneakers safe to go in my 200 gallon I’ve seen it done on tanked??

  137. avatar

    Hello Tye, I wouldn’t recommend using sneakers in an aquarium. The materials used in sneakers aren’t aquarium-safe and would break down under some water conditions and no coatings or coverings will 100% guarantee that moisture would not reach the sneakers. You can contact the Tanked staff for more information on what they did to the shoes before using them but I would disagree with using them at all in an aquarium.

  138. avatar

    Can I use a laminated sign in my tank?

  139. avatar

    Hi Ashlie, A laminated sign is usually fine as a background but I wouldn’t recommend using it completely submerged underwater…water tends to be able to be able to seep within the lamination over time. It will usually last longer if you double-laminate it (laminate it once, cut it out with a laminated seam around the edge, laminate it again and repeat) but it may not last over a long period of time.

  140. avatar

    Hello Eileen, thanks for all of the info, it has been invaluable. I do have a follow-on question from an answer provided back in March 2016. The answer stated using “DryLok, a latex-based waterproof concrete”

    Do you mean DryLok Fast Plug? It is the only concrete that I see, and it doesn’t state it is latex. Just wanted to make sure.

    Thanks for all your help!

  141. avatar

    Hello David, Glad this information has been helpful to you! The DryLok we are referring to here is the Latex formula of Drylok. It is not concrete, but has some sand in the mix. This is what gives it a textured finish, and hides all of the foam used to create such structures. (http://www.drylok.com/formulas/latex-base-drylok-masonry-waterproofer/ ) The drylok can be tinted, or can be painted over once cured. It is used over foam to give it strength and protect it. The Drylok fast plug, is hydrolic concrete, that is used to fill cracks and holes in concrete walls or floors, this sets fast and expands a little as it sets to seal holes.

  142. avatar

    Hi everyone! My name is Cat, and I am brand new to blogging as well as to this blog.

    I am trying to inquire as to whether I can use NEON NAIL POLISH, (or any colored nail polish) on a set of artificial coral aquarium decorations that I have had for a while to enhance the color of them. According to what I have read already, it says that CLEAR nail polish is safe for a freshwater fishtank use.

    I am always redecorating my tanks and changing them up especially for the holidays. I bought some different colored “black light” neon colored grasses to add to them, but I’m wanting to wait for some feedback from y’all.

    Would someone be kind enough as to let me know if that would be safe?
    Thanks very much,

  143. avatar

    Hi Cat, Yes, you can use nail polish in an aquarium! We’ve use it at our store to create custom number plugs inside of saltwater systems. We’ve found that the color tends to fade over time but any enamel paint like nail polish or enamel model paint is safe and fairly durable once it has cured and dried completely.

  144. avatar

    Thank you very much for your help, I appreciate it!

  145. avatar

    I just received a couple of petco aquarium pieces for Christmas and the glaze is crazed. Moreso on one than the other. Is it safe to use? Thanks!

  146. avatar

    Hello Bernadette, Do you know what they are made out of, or do they have any warnings on them against use if broken or underwater? If they were sold as actual aquarium ornaments, they should still be fine to use even with small cracks, but you may want to check with Petco or with the ornament manufacturer to be sure.

  147. avatar

    They’re ceramic, that’s all I know. But they were sold as actual aquarium ornaments. I’ll try and find the manufacturer to contact them. Thanks! I appreciate your help!!

  148. avatar

    I have used sculpy for years in my tank. just make sure it is baked correctly

  149. avatar

    Hi, I had a couple of questions that I didn’t read anywhere else.
    I have a 40 gallon tank for my red eared slider turtle and I’m trying to make him a cave to hide in. Would a new Folgers plastic jar be okay? I know you said no decals but I can’t figure out how to get these off, so maybe they won’t hurt?
    Also, I was hoping to hang something and wanted to use twine. Is that suitable, it might get a little wet, not sure how much. Thanks in advance. I really enjoyed reading all your Q&As.

  150. avatar

    Hi Rebecca, Glad you are enjoying the thread…everyone keeps coming up with lots of new ideas to try! The plastic container itself should be fine. I would remove the label first though. Without seeing it, its hard to say the best way to remove it since the different brands use different types (and I’m a K-cup user myself) but you can try Google for some different methods. I did a quick search and found this method for removing difficult labels or this one for removing printed-on labels. An unglazed terra cotta pot like this one from Michael’s are also good for making caves as are plain PVC pipes…we use tons of PVC tubes in our retail store tanks here.

    Any twine make with natural fibers might be risky. If it gets wet, it may weaken or stretch over time. Depending what you are tying and where, you could try a monofilament like fishing line…its strong, can hold up underwater and us usually transparent. A lot of aquarium decor like these floating rocks use nylon line to hold them in place.

    Hope that helps!

  151. avatar

    Do you have any experience with building tunnels out of PVC covered with fiberglass resin or body fillers like Bondo to create a log look finish?

  152. avatar

    Hi Bob, Resin is usually safe once it is fully cured and as long as it is very well-mixed. If it isn’t mixed properly, it won’t fully cure but once it is allowed to completely cured, it should be safe for the aquarium.

  153. avatar

    I was browsing through your website and noticed that there were a lot of questions regarding fish friendly material for inside the aquariums. I am making my own 3D Rock background for my 85 gal aquarium. I watched a lot of videos to get some ideas and then did my own research on what material should be used and what should not be used. For the rock formations you want to use the standard white styrofoam or insulfoam available at Home Depot or Lowes. To glue the pieces together you want to use an aquarium safe silicone and nothing else.it’s a little pricey but it’s called aquarium safe for a reason. The other 100% silicones that are out there are sealants only and are not mention to be submerged in water or may have a mold inhibited which WILL KILL your fresh, some of them will even tell you in fine print ( not for use in aquariums). These silicones may also after awhile break down when submerged in water. I then coated my styrofoam with Laticrete thin set mortar.( 3 light coats ) It’s a product used in pools and once cured ( in 2 weeks ) is safe , as per my confirmation with the manufacture themselves. Then I will seal it with an enamel clear coat to keep the colors from fading. Let’s do it right the first time. Hope this has been helpful to you fellow diy’s

  154. avatar

    Hello Anonymous, Thank you for sharing. Using styrofoam to create a background can be very effective if done properly and with the correct materials.

  155. avatar

    Hi, My son and I are trying to diy some tank dividers for freshwater aquariums (bettas). My question is this: I got a hold of a large vinyl banner (printed for ikea) that I would like to use. While I can find reams of information on rigid vinyl I have not been able to locate any information on whether or not a vinyl banner material would be safe. Would you happen to know and or have any information on this?

  156. avatar

    I’m getting ready to set up a small 10 gallon tank. The pieces I would like to use are novelties in my room. I was wondering would Clear “FlexSeal” the rubber sealant they are advising on TV work to make them fish safe? Fresh water tank

  157. avatar

    Great post.. I’ve been doing research I want to make a model car themed aquarium using plastic models. When I asked on other groups I get mixed answers. Do you think plastic model cars would be safe once cleaned using aquarium glue to put them together? They make color molded cars or I could use safe paint what would be best? Thank you for your time.

  158. avatar

    Great post… Do you think plastic model cars would be safe? I’ve been told the plastic will leak toxins into the water. Thank you for your time

  159. avatar

    Hi David, Glad you are enjoying this post! Plastic is usually safe and should be fine in an aquarium as long as there are no metal parts like the wheel axils. For paints, enamel paints like nail polish or model paints are safe once they are completely cured and dried. I would avoid any stickers or decals. Good luck!

  160. avatar

    Hi Alicia, I don’t have any experience using it in aquariums personally, but according to the FAQs section of the FlexSeal website (http://www.flexsealproducts.com), they claim the FlexSeal Liquid is safe for fish and plants. They do not recommend using FlexSeal Aerosol for use on containers for drinking water so I wouldn’t recommend using it in your aquarium. The FlexShot states that it has not been tested for safety with potable (drinkable) liquids and it does state that it contains a mildew fungicide so I would NOT recommend using that in an aquarium.

  161. avatar

    Hi Jacqueline, That’s a new one…I don’t think I’ve heard of anyone trying that material before! From what I’ve been able to find, I’d say it would depend on the specific material and manufacturer. There seems to be a very wide range of materials used to make banner material like that and I wouldn’t consider some of them to be safe. Aside from the material itself, I would be concerned about the material blocking water flow as well. How large is the tank you are trying to divide? If it isn’t extremely large, you could try plastic canvas like this product from Michael’s crafts. It is usually in the yarn/needlepoint section and is pretty cheap, easy to cut, available in lots of colors and safe in fish tanks. We actually used clear sheets to create floating lids in our retail store. Since it does float, you would have to weigh it down or anchor it in your tank to create a divider but it would be easy to use and still allow plenty of water flow.

  162. avatar

    Thank you so much for your response, Eileen. I greatly appreciate a more professional opinion based in knowledge. As for our dividers – I continued trying to research and all I could find had me concluding its safety would be highly questionable. So I went out yesterday and purchased craft mesh which I have managed to fashion into dividers that in the end I am quite pleased with… as are our fish 🙂 bettas – 3 divided tanks (1 x 15 gallon; 2 x 20 gallon long)
    🙂 Sincerely,

  163. avatar

    Glad you found something that worked for you, Jacqueline. That plastic canvas craft mesh is some wonderfully versatile stuff for aquariums!

  164. avatar

    Hello, I am a saltwater enthusiast, and also a musician. I am creating a music room, and want to put a tall tank in the corner. Is there any way that I could put one of my old clarinets in it?

  165. avatar

    Hi Ben, Interesting idea…I used to play clarinet myself. If you can find a completely plastic or glass clarinet, it would be safe but I wouldn’t add one that has any metal in the keys or with a wooden body; it wouldn’t hold up underwater and would start to rust or decompose, even if laquered or coated. Saltwater tanks with live rock especially would also lead to any surfaces becoming encrusted with coralline algae. If you find an image you like, you could use it as a background for the tank or look for something like a latex decal for the front of the tank to get some musical details onto the tank.

  166. avatar

    Hello,my name is kim.I wish to make an enquiry about a little project I’m conducting.I’m trying to build a self sustaining aquarium using an old rusted wheelbarrow
    I have already painted it using a black paint commonly used to prevent rusting of metals.Is it safe to continue or should I add something else to ensure my fishes safety?

  167. avatar

    Hello Kim, I see that you’ve asked a similar question on two of our blogs so I’ll add this reply to both. As we discussed in both blogs, metal is not safe and nothing will make an unsafe material 100% safe for fish. You can try using a pond liner or coating the wheelbarrow in a fish-safe material like the FlexSeal Liquid discussed in a previous comment but keep in mind that any moisture that reaches the metal can cause it to leach into the water. Rusted metal will also because structurally unsafe over time and can collapse or become too weak to hold water.

  168. avatar

    I found a cool garden gnome, and i am wondering if its safe for my aquarium?

  169. avatar

    Hello Anonymous, It would depend on what the gnome is made out of. I would recommend figuring out what the material is and reading through this blog and the other 2 blogs in this series to see if it is a safe material for your tank. You can also test it in a bucket of water with similar conditions as your tank and see how it holds up as we discussed in this series.

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About Eileen Daub

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Marine Biologist/Aquatic Husbandry Manager I was one of those kids who said "I want to be a marine biologist when I grow up!"....except then I actually became one. After a brief time at the United States Coast Guard Academy, I graduated from Coastal Carolina University in Myrtle Beach, South Carolina in 2004. Since then, I've been a marine biologist at That Fish Place - That Pet Place, along with a Fish Room supervisor, copywriter, livestock inventory controller, livestock mail-order supervisor and other duties here and there. I also spent eight seasons as a professional actress with the Pennsylvania Renaissance Faire and in other local roles. If that isn't bad enough, I'm a proud Crazy Hockey Fan (go Flyers and go Hershey Bears!).