Home | Aquarium Equipment | Aquarium Gravel and Substrate vs Bare-Bottom tanks: Pros and Cons

Aquarium Gravel and Substrate vs Bare-Bottom tanks: Pros and Cons

One of the first purchases most aquarists will make for a new aquarium, be it freshwater, saltwater, reef, discus, goldfish, cichlid or any other – is the gravel and substrate. It could be sand, crushed coral, Fluorite, neon pink pebbles, glass marbles or countless other materials  but it all tends to be the very first thing to go into an empty aquariums. But….why? Do you really need it? Are there alternatives? Much like the eternal home decorating debate of hardwood-versus-carpets, the battle brews among aquarists over what covers the bottom of their aquariums, a layer of substrate or nothing at all.

 

So why has substrate become such an integral part of the aquarium culture, and why are some aquarists now looking past it in favor of the bare glass or acrylic bottom of their aquariums? Much of it has to do with our understanding of the aquarium ecosystem now over what we knew years or even decades ago. Even as recently as five or ten years ago, undergravel filters were thought as indispensable for all types of aquariums and as such, gravel was thought vital to their function. We’ve come a long way with filtration technology since then, and we’ve also come a long way with understanding how the water chemistry in our aquariums functions. Alternatives and advancements have made the old undergravel systems nearly obsolete and the aquarium gravel that went on top of them is become more of an Option instead of a Requirement.

 

That said, how do you make the choice? Like so many other parts of our hobby, it comes down to personal preference and your goals. Bare-bottom tanks are becoming more common and have their benefits of substrated tank and vice versa; substrate is still a better choice than going bare for some other types of tanks. Weigh your options carefully before you choose which one is right for you. We’ll go over a head-to-head comparison in the major factors to consider to help you make your decision.

Cleaning a Fish Tank

 

The ever-iconic Gravel Vacuum

The ever-iconic Gravel Vacuum

An aquarium that is easy to clean and easy to care for is the dream of most aquarists. Bare-bottom tanks win this category easily. Ever wrestle with starting the siphon on a gravel vacuum, then have it clog up repeatedly with gravel when you are cleaning? With a bare-bottom tank, a gravel vacuum isn’t needed; you can just use tubing to vacuum up any waste sitting on the bottom of the tank and water pumps or powerheads can be used to circulate the water underneath and behind the rockwork more efficiently. It can be a lot easier to scrub algae off of the glass bottom and sides without having to worry about missing some at the gravel line or getting bits of sand stuck in your scrubber as well. For tanks like reef aquariums with lots of rockwork, debris and detritus can get stuck under the rocks or in the back where your vacuum cant reach as well, causing the nitrate levels and algae blooms to increase. While not as vital in, say, a freshwater community tank, nitrate and algae can spell Doom (and Headaches) in a reef tank.

 

Aesthetics & Natural Environments

 

IMG_4312

A natural planted freshwater nano-tank

I have to give this one to Substrate. Surprisingly, flat panes of glass or acrylics just aren’t found at the bottom of most environments in the wild. Natural environments have sand, or mud, or pebbles or some other natural material. Besides just plain looking more natural, some animals also need this substrate to live normal lives. Some fish and snails bury themselves in it or find their food in it. Timid animals need it to hide or camoflauge themselves and in some specialized ecosystems, the substrate plays a vital role in the water chemistry. Most live aquarium plants won’t survive without a substrate to root into. Having a substrate also provides many more options in changing the look of the aquarium, whether its a natural substrate or a decorative one.

 

Aquarium Water Chemistry

 

This one is an even draw; both having substrate or having a bare-bottom can negatively and positively affect the water chemistry in an aquarium. Some substrates like crushed coral can buffer the pH and hardness of the water. For a saltwater tank with a target pH around 8.0-8.4, this is a good things. For a tropical tank with a target pH around 6.0-7.0, maybe not so much. A Flouorite substrate for planted freshwater tanks can give the plants some much-needed minerals and nutrients through their roots that a bare-bottomed tank can’t give them.

 

As much as this exchange helps, any waste that can get trapped in the substrate can hurt the tank. If waste becomes trapped, it will decompose and increase nitrate, phosphates, ammonia and other negative levels which can lead to fish illness and algae blooms. As we mentioned before, this waste is much easier to get rid of in a bare-bottomed tank.

 

Microinverts, hitckhikers and other “bonus” tankmates

 

IMG_2091

Our bare-bottomed 700 gallon store display tank

Unexpected new arrivals like bristleworms can be the ban of a saltwater aquarist’s existance, and tiny little nuisance snails or flatworms can harass a freshwater aquarists to tears. Most of these critters live or reproduce to some extent within the substrate and getting rid of the substrate to go bare-bottom will help get rid of them. Unfortunately, it will also get rid of the good critters like copepods and amphipods that can provide a natural food source to some of the pickiest fish and inverts. If you are making your choice to go bare-bottom to get rid of the nuisance critters, weigh the needs of the rest of your tank carefully to see if they can do without the good to get rid of the bad.

 

The (Bare-)Bottom Line

 

Choosing whether to add substrate to your aquarium or stick with the bare tank ultimately rests on you. Most aquariums will survive either way but one choice may be more successful than others. In our store, we have both bare-bottom tanks and tanks with substrate among our display tanks as well as the tanks we sell fish out of. Stocking these tanks is determined by the needs of the fish and the care that they need. Generally, coral-only reef tanks can go bare, planted freshwater tanks can’t; freshwater fish-only tanks might not need it but saltwater fish-only tanks (or fish-only with live rock) will do better with it. If you can’t decide which way will be more successful for you, we’d be happy to help you make the best decision for you and the success of your aquarium.

26 comments

  1. avatar

    Hello Eileen. Thank you for all the help regarding resin and plastic aquarium ornaments. Now I have a question about the substrate. I want to add to my marine aquarium a yellow “coris” wrasse and I have an aragonite substrate in the neighborhood of 1.5 to 2 mm grain size. I have being doing some research on the web about the right kind of substrate for that fish. Some places mention it needs fine sand to bury itself in there to sleep and other places say it doesn’t need sand at all. Do you believe the substrate that I have will be good enough for the wrasse to bury itself? Happy Holidays.

  2. avatar

    Hello Arturo, I’m assuming that the wrasse you are referring to is the Canary Wrasse? These wrasses do much better with substrate to bury into when threatened and to graze food like copepods from. Fine sand with smooth edges is much better for them and their delicate skin than coarse substrates but larger wrasses should be fine with 1.5-2mm grains as long as they don’t have sharp or jagged edges.

  3. avatar

    Thank you for your reply Eileen. That is correct, I’m referring to the canary wrasse. Since I have this aragonite substrate of about 1.5 to 2 mm grain size, I would´t want to buy fine aragonite sand because it is expensive. I’m considering fine silica sand. Some sites claim it may cause problems with diatoms in a marine aquarium and some mention it may be OK to use since it is probably inert. I would like to mix the coarse aragonite I have with silica sand for the benefit of the canary wrasse. Do you think that would be a good solution? Regards.

  4. avatar

    Hello Arturo, Silica sand is typically safe. It does require a lot of rinsing and can make the tank cloudy if not rinsed enough and until it settles, but shouldn’t cause a diatom bloom in itself. Some aquarists see a diatomaceous algae bloom after adding sand but that is more likely caused by the tank going through the nitrogen cycle again after an old substrate (and the bacteria on and in it) has been removed or because the diatoms are easier to see on top of the very light and fine sand rather than on the darker aragonite where it can settle into cracks. Unless you keep the sand and aragonite separated, there wouldn’t be much benefit in using both since they will mix together and the wrasse would still have to bury within the coarser substrate as well as the sand.

  5. avatar

    Ellen,

    The only reason I am considering removing my gravel substrate and go to a bare bottom tank is a horrible fishy smell I am getting only when I do a water change? My tank is salt water with living rocks, some coral Fuzzy Mushrooms, Tangs and Clownfish and pretty large Anenome. It is 110 gallon and it has been established for 7 years. I change 10 gallons every 2 weeks using RO water. The water smells nice and earthy but something has changed. The last 3 times I did a water change, the smell of fish is horrible. The water smells fine until I vacuum the gravel. My glass also has a brownish oily substance forming in it that was never there before. That brings me to my question of should I remove the substrate? I don’t really have any local saltwater experts but one that I talked to an hour away said it might be accumulated waste under the substrate? Help!!

    Randy Nielsen

  6. avatar

    Hello Randy, How deep is your substrate and do you have anything under it like an undergravel filter? Have you tested your water quality, and what are the values for Ammonia, Nitrite, Nitrate, pH and Phosphate? When you do your water changes, do you regularly siphon the gravel or is that something you only started doing when you noticed this problem? It sounds like your substrate has gone anoxic, meaning that oxygen can’t penetrate it and the substrate is trapping waste material and gases. This can sometimes happen if the substrate bed is too deep or isn’t aerated enough or if there are pockets underneath it that allow gas to become trapped and build up. Without knowing more about the water chemistry and filtration, it is difficult to recommend a good next-step for you.

  7. avatar

    I thought alot of the beneficial bacteria was in the substrate?

  8. avatar

    Hello John, Any surfaces in the tank including substrate and decorations can play host to the beneficial bacteria but it is also in the water itself as well as in the filtration. For tanks without substrate, adding additional biological media to the filtration system is a good idea.

  9. avatar

    Ok i modified my aquaclears and put ceramic rings and also added floss ive been really thinking about going bare bottom, what about my ghost knife they seem to like the gravel would it bother them much if its bare bottom?

  10. avatar

    Hi John, Ghost Knifefish tend to do best with a fine-grained, smooth sandy substrate. I wouldn’t say that it is essential for them but they seem to be more comfortable with it. If you remove the substrate, just be sure that it still has lots of places to hide so it doesn’t become stressed.

  11. avatar

    They have many places to hide but they dont, they are not scared they play in my hand and lay in it when i cup my hand same as my rope fish

  12. avatar

    Hi

    I’m rescuing some fish from someone at work that was terminated, and left their fish behind. The gravel is disgusting, so I’m thinking of just going bare bottom. However, there is a Pictus Cat, and a Pleco. I will have wood in there for the pleco, but I’m worried about the cat. Will the cat be fine for two weeks while I wait to put him in with my South American tank that does have substrate?

  13. avatar

    Hi Bradley, The Pictus Catfish should be fine in a bare-bottom tank for awhile. They are far better in tanks without substrate than in tanks with an unsuitable substrate.

  14. avatar

    With s 100 gal goldfish and sword clown pleco tank I have it as a bare bottom tank it does have live plants well trying to have live plants I should say it dirt and pots with little gravel on top to keep most of dirt in its place my tank also has lots of kinds of driftwood of course the clowns my tank has a turn over in filtration of 10 times my stocking is 5 sword clown pleco two common shubunkis goldfish 6 inches total length counting longfins and a small oranda goldfish plants dwarf Lilly Java fern Java nano onion plant moss here and there no co2 little plant fertilizer and all out with my lighting “grow lights” anyways though just few months in trying to grow plants chose hardy ones not too much growth in plants any advise should I substrate the whole tank I know I have some salid eating fish but I happy with them lol just wanna have both my fish and plant growth any advise take good and bad

  15. avatar

    Hello Lee, I’m afraid I don’t understand what your question is. Live plants like most of those you mentioned do need substrate and goldfish will eat live plants.

  16. avatar

    I have these plants in substrate they are in clay pots with dirt as a substrate in the pots for plants with small fertilizer pellet in dirt with gravel layer on top my ? Would be should I turn my hole bare bottom tank into substrate out of the pots or dies that really matter rather way and also yes goldfish eat plants but people keep them in ponds even over stocked ponds with plants so I know it can be done in a fish tank as well so I guess just looking for advise from people who have kept both plants and goldfish together as fare as what kind plants substrate used mostly hardy plant ideas that maybe can rather grow fast or tough for goldfish to shred and eat or maybe I’m doing something wrong with my tank setup so just looking for any advise on goldfish and live plants

  17. avatar

    Hello Lee, An aquarium plant substrate would be best. Using dirt or a fertilizer that is not for aquariums can be harmful to your plants and fish. Goldfish will eat any kind of plants but thicker-leafed plants like Anubias may stand a better chance than more delicate-leafed plants.

  18. avatar

    I using a pond plant slow release fertilizer tab maybe I will try a different substrate then dirt Anubias what is your recommendation as of lighting I’m using T8 bulbs pink spectrum 2 maybe I need more lighting idk

  19. avatar

    Hi Lee, If you are using T8 lighting, around a 6700K spectrum is best for freshwater plants and the bulbs should be changed at least every 6-8 months.

  20. avatar

    Ya they higher around 10000k all added up anyways is this to much lighting

  21. avatar

    The Kelvin rating is a measure of color…it can’t be added up. The bulbs are manufactured to a certain color temperature so 2 6700K bulbs do not equal 13,400K, for example…it equals 2 6700K bulbs.We have a number of Aquarium Lighting Basics articles on our website that you can read and learn more about lighting as well as a lot of other topcs, including goldfish and plant basics.

  22. avatar

    Hello Eileen. First I would like to thank you for all your help and I wish you a happy Thanksgiving. This post is about my marine aquarium. It used to be a freshwater one and I did not have any problems with algae. When I turned it into saltwater the problems with algae started. I was using a product that allows one not to change the water for a year. Unfortunately, despite the fact that the product kept nitrates at 0 ppm and phosphates at 0.25 ppm, the aquarium had and still has a big problem with green and brown algae covering everything, the substrate, glass, heathers, pumps and ornaments. The equipment I have is a HOB filter and a denitrator. I have been researching about things like protein skimmers and UV filters in forums and other sites. I know that a UV filter won’t get rid of algae that sticks to surfaces, however, when I clean the aquarium some of the algae floats free on the water so maybe then such a filter could help. Now I have been performing 10 % water changes every two weeks without success removing the algae. I added to the aquarium back in February a new LED light strip designed for marine aquariums, so I’m not sure if that could help with the problem. My aquarium is a fish only 60 gallon tank and only has 5 small fish and I do not overfeed them. I’m puzzled about the fact that there are no nitrates and almost no phosphates yet is a very bad infestation of green and brown algae, maybe silicates are the problem?. I was using tap water when the aquarium was fresh water with no problems and I continue to use it now that it is saltwater. I cannot afford a RO system, so I hope I could solve the problem by still using tap water. Do you think a protein skimmer or a UV filter would help? Kind regards.

  23. avatar

    Hi Arturo, A protein skimmer would definitely help in a saltwater tank to get rid of any organics in the water. I would recommend one for any saltwater aquarium. UV sterilizers are effective but only help with anything in the water itself. If it isn’t your water itself that is “green”, it probably won’t help that particular issue too much, especially in a tank as small as yours. Both a protein skimmer and UV sterilizer will be at least around the cost of an RO Unit however. Is the algae you are seeing like a slime coating or is it like a coating of very fine hair? A thick slime coat would be cyanobacteria, not a true algae but behaves in a similar way. You can read more about that in our blog entry here. If it is very fine hair, then you are likely dealing with a nuisance algae called Bryopsis. That stuff is, unfortunately, much tougher to control. If you would like to send in some photos of your algae issues, I can take a look at it for you and help you identify it. I would also recommend upgrading your filter. HOB filters aren’t the best for saltwater tanks over about 20-30 gallons or so and a wet/dry or canister filter would give you much better flow and filtration. I don’t recommend a product like the one you mentioned to eliminate water changes; those “magic wand” type products can cause more issues than regular maintenance, in my opinion. Happy Thanksgiving!

  24. avatar

    Thank you for your reply Eileen. What I have is a slime coating, some areas are green and most of it is brown. I used to have most everything coated in black cyanobacteria and back then I used a slime remover product and it worked very well to remove the problem, even from the substrate. Later the aquarium developed the green and brown coating, so I tried that kind of product again, but this time it did not work. That is why I think is algae and maybe diatoms. I will check out your blog entry. I can certainly send you photos of the problem, to what email: marinebioblog@thatpetplace.com?

  25. avatar

    Hi Arturo, You can send the photos directly to me at edaub@thatpetplace.com. With only a HOB filter, I’d be more inclined to think that the slime coating is cyanobacteria, possibly as a result of low water flow. You can try adding a small powerhead lower in the tank to improve water flow if you are not able to upgrade your filtration. A diatomaceous algae bloom would clear up on its own over time and would be a very thin tan coating. Also, how long is your tank lit every day (from both your LED fixture and bright ambient lighting from the room, if any)?

  26. avatar

    Thank you Eileen. The aquarium is not close to a window and virtually no sunlight gets to the tank and the LEDs are on for eight hours. I will send you photos soon. I appreciate all your help.

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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!).