What is Anaerobic Bacteria and does it consume Nitrates?

[Samuel]

Hearing good and bad things about anaerobic bacteria in an aquarium and am curious to learn about it. What is it and what experiences have you had with anaerobic bacteria?

(Substrate from my cichlid tank)

[CJs Aquatics]

This is a highly debated, very advanced topic in my opinion. I guess in simplest terms, anaerobic bacteria as I’ve understood it is bacteria that doesn’t need oxygen to grow and colonize. I would assume it’s present in deep enough substrates/ possibly in plenum set ups, very niche aquaria. I am far from an expert on the topic as it can get very scientific however I have been led to believe it does utilize nitrates for some processes. Fact check this with the forum however this has been my simple understanding and I wanted to at least address your question. The tank looks great by the way, hope this helps some…

[Gannon]

Yes it can, but usually isnt a big player in an aquarium "ecosystem"

[Biotope Biologist]

Yes a very complex topic indeed. Basically I think we have come to the conclusion that aquariums are too small scale to make use of the processes but here is a more lengthy talk about it:

 

[Odd Duck]

This is indeed a very complex topic and not understood nearly well enough when it comes to aquariums.  Anaerobic bacteria means bacteria that can live despite having little access to oxygen.  In other words, they metabolize things very differently than aerobic or oxygen dependent bacteria.  What this encompasses is hundreds, or more likely thousands, of different species of bacteria.  What it means in aquariums is that there can be many, many different species that use and produce many different compounds as part of their metabolic processes.

So some anaerobic bacteria may be very toxic in an aquarium or produce very toxic substances (like hydrogen sulfide gas - the source of the rotten egg odor that you’ll sometimes smell if you stir up a section of previously undisturbed substrate and it releases gas bubbles.  Some anaerobic bacteria will “eat” nitrates and release N2 (nitrogen gas) which is pretty harmless in the typical amount produced and we breathe every day since it’s around 78% of the atmosphere.  As long as your tank has reasonably normal circulation with no oil or protein film on the surface of the water, your fish are safe from any small amount of nitrogen produced in your tank.

If we could consistently produce just the right anaerobic conditions in the tank on a large enough scale, then any nitrates would be consumed by the bacteria and released as nitrogen gas (N2) and dissipate into the air and we wouldn’t have to do water changes to control nitrate levels.  The reality is that the perfect environment is darned difficult to produce and you’re as likely to get some nasty bacteria producing toxic hydrogen sulfide gas that can knock out your tank inhabitants instead of helping.  Plus the surface area needed to build up enough of the “right” bacteria for a typical tank is massive and difficult to achieve without having another, even larger, linked tank dedicated to only the nitrate eating bacteria.  The Walstad book talks a bit about this and some say Walstad method can do this.  I have my doubts.

The boots on the ground issue is that every single tank is different with different substrates, different plants, different fish, different feeding, etc.  Even if you set up several tanks as identical as possible, individual plants or fish or shrimp, etc, might grow and reproduce at different rates and very shortly there would be differences between the tanks.  So study results would be nearly impossible to reproduce.  It’s also darn difficult to determine exactly which species are doing what, not to mention that some behave differently in combination, or at different population densities.

The more we learn about bacteria behavior, the more we realize how much we don’t know.  There are new dog and cat foods coming out all the time with changes in their formulation to encourage certain types of bacteria to grow in the gut to help support the immune system, to help control weight, to help maximize overall gut health, etc, etc.  And that’s in pretty well studied animals where funding is far more available.  Aquarium bacteria need far more study but in many ways the “organism” being studied (the entire tank is the organism in this case) is far more complex than a relatively “simple” dog or cat.

[Huckleberry]

Check out father fish.

[JettsPapa]

On 2/22/2023 at 12:42 PM, Pepere said:

it has always seemed to me the labor involved is greater than the labor one is seeking to avoid…

Water changes have more benefit than simple nitrate reduction.  Dilutes or replenishes minerals, removal of stunting hormones or plant allelochemicals. If you are set up well for a water change it need not be onerous. . . 

That reminds me of a YouTube video I saw sometime ago.  I can't remember the guy who produced it, but he recommended not testing water if you think it might need a water change.  He said by the time you get done testing you could be half through with the water change, so just go ahead and do the water change.  It can't hurt anything.

[BlueLineAquaticsSC]

I don’t know much, except that this is what “deep sand bed” set ups are trying to accomplish. I think Cory talked in a video about it before and stated you need a minimum of 4” substrate to start colonizing the bacteria. I kept a tank with a 5” bed and never could tell any difference, but it was also full of MTS and cichlids so maybe the constant stirring prevented bacteria growth anyway.

[Samuel]

Thanks for all the responses, definitely starting to understand more about it!