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.

 

Adhesives

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  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.

 

Paint

• 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.

 

Decorations

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.

•  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!

•  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!