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Interesting, it seems sponge filters are the absolute best at processing ammonia and nitrite, according to this person's research.


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Found this page some time ago, perhaps some of you might know it. Most of the articles are from a few years ago, but the author has recent updates on them. There's lots of info there but this one in particular caught my eye:


Some highlights of the experiment:

  • An empty aquarium with a filter without filter media can break down at least the same amount of ammoniacal nitrogen as an aquarium with a handful of high-quality filter media (Seachem Matrix alias pumice) in 24 hours.
  • The use of filter media in the filter is most likely unnecessary (at least in terms of nitrification) in a planted aquarium with a reasonable fish stock.
  • The importance of filtration (or filter media) appears to be overestimated (at least in terms of nitrification). It is also quite possible that many filters may increase ammonium concentration in the aquarium rather than reduce it effectively. Some filters may function as "traps" and producers rather than "degraders" of organic waste.
  • To break down such an extreme concentration of ammoniacal nitrogen as 30 ppm NH3/NH4+ virtually zero filter media is needed. This means that even the minimal amount of nitrifying bacteria that can be produced on ordinary surfaces inside an aquarium, in hoses or in an empty filter, is enough to break down virtually any amount of ammoniacal nitrogen that could occur in a normal planted aquarium.
  • The most effective filter medium in the degradation of ammonia (nitrification) has proved to be an ordinary foam filter called sponge filter**. It managed to break down an incredible 3.15 grams of pure ammonia (70 ppm) in a 12G (45ℓ) aquarium in 24h, which no other filter (or filter media) tested was able to manage.**For an idea: This amount of ammonia is produced by more than 10 kg of adult Neon Tetras in 24 hours. 

    We constantly hear from seasoned fishkeepers that most likely we don't even need filtering media or even a filter, as our tanks are already full with bacteria (with reasonable fish stocking), and here's the proof of it.

Among other amazing finds is that nitrifying bacteria living on the biofilm of the filters themselves also take a considerable role in biofiltration. Author completely cleaned the surfaces of the canister filter, removing every bit of biofilm BUT placed cycled media. The media wasn't able to completely remove the ammonia concentration by itself in 24hrs, so in conclussion the biofilm plays a part too! Don't scrub it off!

I urge you to read the entire article, it's really interesting.

Thoughts? Criticism on the experiments?

Edited by HenryC
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I am currently running nine aquariums. I don’t have any filters in any of the aquariums including the 500 gallon aquarium. All the tanks have plants in them, and my assumption is this is what does most of the filtration along with the biofilm in the aquarium.

I’m not against filters, it’s just that I only run them when I need them. And then it is usually a sponge filter.

I think the reason I can get away with not using filters is low fish populations.

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  • 4 weeks later...

Fwiw when i was a kid i had a 2g tank with no plants, 1 betta and 3 tetras using no filter but just the same ceramic airstone and kept that going for about 5 years despite having no idea what i was doing. I never used any chemical treatments (that i can remember) and always fed them Tetra tropical flakes. And the substrate was about 2 inches of blue gravel. I don't remember how often i did water changes but i wanna say it was like 50% once a month. 


That being said, my understanding is that part of the purpose of filter media (specifically sponge-type whether its a sponge filter, a prefilter for an intake, or a sponge pad) aside from catching larger more tangible pieces of debris is also to provide additional surface area for that nitrifying biofilm to exist on. 

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My understanding is, that the nitrites are taken care of by aerobic bacteria, that can be attached to pretty much anything in the aquarium, including the inside of the aquarium itself. 

Nitrates however are processed by anaerobic bacteria, and plants of course. If one doesn't have enough plants and the right kind of bacteria, water changes will be needed. It can be almost impossible to have the anaerobic bacteria accessing the tank water in other places than inside filter media, through which the entire volume of water is cycled (assuming proper flow and circulation in the aquarium). And even then it requires certain kind of porous filter media inside which the water first is processed by the aerobic bacteria on and near the surface, and then by the anaerobic bacteria deeper inside. A sponge filter will have no anaerobic bacteria, but it will have decent amount of room for aerobic bacteria, depending on the size of the pores.

None of that you need to worry with enough plants removing the nutrients, or enough water changes. Water changes of course can stress fish, so limiting them was my goal. Maybe I'm also lazy.. Anyway, I went with a large external filter, and once the bacteria had established itself inside, it does help. And plants on top of that, life is even better and easier 🙂

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