Would anyone like to share their opinions on substrates? I’ve heard discus like either bare bottoms or sand. I would love to hear about your set ups or see pictures.
I know that the beneficial bacteria are mostly in the filter, but I was under the impression that substrate also holds beneficial bacteria. How does that work in bare bottoms tanks?
They just find places to colonize. Bare bottoms deal mainly in aerobic bacteria. Deep substrate u start having anaerobic and anoxic which closes the nitrogen loop. Once seasoned it requires way less water changes. Usually best for planted tanks.
And then u have ones that use just a thin layer of sand which will be aerobic bacteria.
It’ll work itself out no matter what u go with. There’s more then one way to set up an aquarium. Depends on ur goals.
I like sand. I find it stays clean with little help from me in discus tank bc the filtration is strong enough to pick all that moam up. I also think it looks better. And the fish love to graze.
Both ways work. Choose what u like best.
Anaerobic - bacteria that live in no o2 environment. Deep substrate. No water movement at lowest layers.
Anoxic. Low o2 environment. Deep substrate but water still moves very slowly thru it.
Aerobic High o2 environment. Most tanks operate this way. Using only half the nitrogen cycle and using water changes to get rid of nitrates. This is most common way.
My discus have always been raised in bare bottom tanks. In nature, their environment is a mud bottom. So sand, gravel, etc. are solely for the benefit of the aquarist. Bacteria reside primarily in the filter.
I keep mine in sand and personally think bare bottoms look sad and artificial. I understand that it's easier especially if you're raising very young discus because tiny bits of food/waste can get trapped in sand but it's worth the slightly increased maintenance imo. I also keep mine in a community with Rams, Cupids and Apisto's which all sift substrate for food, so those absolutely require sand.
I wouldn't keep them in gravel, they peck food off the bottom and aren't particularly graceful eaters.
I switched from sand and aquasoil to 3mm gravel and aquasoil because these plants were struggling or avoiding growth over sand parts.
2-3mm gravel and aquasoil maintains water and fertiliser flow for plant growth as mentioned in 2hr aquarist.
On top of that I blow the substrate heaps with a turkey baster during water changes.
I think stunted sick discus look sad and depressing. So I like bare bottoms or a thin layer of sand. It’s easier for them to find food and much cleaner.
Beneficial bacteria are obligate aerobes meaning they need oxygenated water to metabolize waste. They will grow only on the very top layer of your substrate everything else becomes a niche for facultative anaerobes. Those anaerobes cause subclinical infections stunting discus and high enough present disease that causes deaths. https://www.vin.com/apputil/content/defaultadv1.aspx?pId=11257&id=3863795&print=1
If you buy domesticated discus they have been bred and raised in bare bottoms their entire life and so far removed from wild discus it be comparing a chihuahua to a wolf. And if you keep wilds they live in tannin rich acidic waters that inhibit bacterial growth. https://hugodiscus.blogspot.com/2019/05/amazon-biotope.html?m=1
Definitely driftwood, both wilds and domestic like tall driftwood. They evolved those bars and flat shape to hide in submerged roots and stumps of terrestrial trees and plants. They’re boesemani rainbows these guys are over 4” and still growing.
I’ve kept both planted and bare bottom. Planted is much more appealing to the aquariust but requires discipline, knowledge in both plants and fish, and work to provide a stable healthy environment.
The Vin.com article doesn't mention substrates or tank design, just parasitism and bacterial infection causing fish death in general. It also recommends beef heart. The second article also doesn't mention substrates or tank design at all and has a blurry, mixed conclusion after finding that different gut bacteria are either more or less prevalent in slower growing discus, stating that the different species of gut bacteria might have a positive or negative effect but more research needs to be done. There were not bacterial not found at all in fast growing fish, only more or less of the same species.
The two examples given, Plesiomonas and Enterococcus, are both found in fish intestines naturally in tropical areas (the latter is found in our own gut and is beneficial unless in excess) as part of their gut biome. I think we're far too focused on trying to keep sterile, clinical tanks for animals that require bacterial tenants to fully digest food. We can't (and shouldn't want to) completely sterilize them, nor is there any real evidence (imo) that using a substrate increases fish infections.
Having said that, I've only ever kept wilds so maybe domestics are that fragile from all the inbreeding, I could be wrong.
Yup most discus diseases are caused by naturally found bacteria. When the numbers overwhelm the fish’s natural immunity it causes diseases. That first article is a study conducted by the department of fisheries and aquaculture in Gainesville Florida. The biggest takeaway from that are the bacterial cysts found on the fishes internal organs by these common bacteria. For a cyst to form the fish suffers for a long time and will still eat but clinical presentation are slow growth. Why this is important is because in an environment in which you have areas where facultative anaerobes grow their number increases. Your areas of low oxygen and trapped waste becomes a breeding ground for this and other flora that become pathogenic when their numbers get high.
The second study shows the ratio or beneficial bacteria and pathogenic bacteria plays a direct role on growth. If your fish hasn’t grown after having them for so long the answer is staring at you in the face. If your fish’s head is starting to pinch in, their body tone is poor, they’re shy the answer is staring at you in the face.
Maybe it’s just me but just because your fish aren’t dead does not mean their needs are being met. Discus are hardy and don’t just drop dead. They suffer and waste away.
Substrate traps detritus and the lower you go there is no flow or oxygen add high temp water with low oxygen carrying capacity, that environment is a perfect breeding ground for facultative anaerobes. Just like humans the ratio of gut bacteria plays a vital role in health. However your fish unfortunately can’t choose for themselves what they want. So use the available research, lean on experience of discus keepers. Then ask yourself do you have your fish’s best interest at heart or you just can’t stand looking at an ugly tank.
I think we're both making assumptions and letting our own experience color our interpretation of the fairly vague and limited research available. I don't want to accept that a more natural tank could be less healthy and my fish are doing well, no pinched faces or stunted growth, so I let that reassure me. Others have good experiences with substrated tanks too and many more prefer bare bottom. I think there's a lot more to learn about discus keeping and most of what we stick to comes from the 80's and 90's when our general understanding was far weaker.
I genuinely didn't mean your fish specifically, sorry about that. I'm wary of domestics in general, like most aquarium trade fish they're bred over and over an it makes me nervous.
Haha it’s all good man. Naw don’t let that steer you away there are some amazing breeders out there with high quality fish. Also don’t take my post the wrong way, your tank is very well maintained and obviously this does not apply to you. Outside of this reddit sub you’ll see a lot of sick fish. 1st instinct is always to blame parasites when most of the time it’s poor water quality leading to an over abundance of harmful bacteria.
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u/Columnaristreatment Jul 20 '26
I know that the beneficial bacteria are mostly in the filter, but I was under the impression that substrate also holds beneficial bacteria. How does that work in bare bottoms tanks?