I have switched all of my foam filters from the cheap ATI foams to the higher quality Poret foam. If you use a either one of these it is doing both mechanical and biological. You cannot prevent this from happening.
What most people do not realizez is that the majority of we think of as mechanical waste is actually organic in nature. Dr. Tanner on Swiss tropicals has a really good article on this here:
https://www.swisstropicals.com/library/aquarium-biofiltration/
But this is the important part in terms of what I stated above.
Biofilms are communities of microorganisms (see below) in which cells are embedded in a self-produced matrix of extracellular polymeric substance (EPS), which is often called “slime”. The cells adhere to each other and/or the surface. Biofilms are a system/network of microorganisms that adapts to environmental conditions. They form on living or non-living surfaces and are prevalent in natural and artificial settings. EPS is a polymeric conglomeration generally composed of extracellular biopolymers in various structural forms. Biofilms are the basis of substrate-bound aquarium biofiltration.
Microbial community & soil biology
The microbial community in soil is diverse in species and highly variable depending on physical, chemical, and animate conditions such as temperature, pH, and the presence of roots for example. In soil, you will find all three domains of live: Archaea, Bacteria, and Eukaryota (animals, algae, fungi, and plants). Archaea and bacteria often co-exist in biofilms and form around particles and in pores of the soil substrate........
Eukaryota: the pore space in soils is full of organisms, some are sizeable such as earthworms and various insects, others are very small such as mites. Fungi are somewhere in the middle, since individual hyphae are tiny (in the micron range), while the whole colony can cover several square miles. Many of these organisms are summarized as detritivores, detritus feeders, or saprophages. They start the decomposition of organics by eating leaves, dead animals, excrements, etc. Their waste in turn is eaten by ever smaller organisms until we reach the true saprotrophs, which digest waste and organic matter by extracellular digestion (fungi but also bacteria and archaea). Saprotrophs release enzymes that break down matter and then absorb its components such as amino- and fatty acids, sugars, etc.
What does that mean for aquarium biofiltration?
Water filtration is teamwork by the members of the substrate microbial community from all domains of life. This is an important conclusion, both for freshwater and marine habitats. The different players form a food web, where
most organisms cannot exist alone but are interdependent. The microbial community varies greatly depending on the availability of foods, pore sizes, and substrates. Soil biofiltration is therefore very plastic, meaning it can cope with a variety of conditions. However, one feature is common.
Natural layers of biofiltration are usually undisturbed for longer periods of time (many weeks and months). In nature, no one squeezes out the debris or rinses the media on a weekly schedule. Occasionally, seasonal floods or rains may “wash” a gravel bed but regular rinsing of the filter media is not happening. The microorganisms eat the debris and the sludge is completely broken down into gases and soluble products that then escape the pore space. Soil biofilters are almost maintenance-free. The released substances are either getting into the atmosphere or are taken up by plants.
For aquarium biofiltration to be most effective, filters should be running undisturbed for as long as possible. Filter media that remain passable and have a variety of pore sizes are best. Given that we like to influence the water parameters depending on the species we keep, and thus make water soft, hard, etc, the filter media should be chemically inert, so that it does not affect the water chemistry by itself.
Author © Stephan M. Tanner, PhD
Basically, since most mechanical waste is organic, it gets sucked into the foam. This happens whether one has foam in a hang-on, a canister, a sump of plain air powerd foam. If it is in the water it can get into the foam.The big difference between nature and out foasm filters is we do not have the bigger organbisms ention above inside the foam. The mechanical waste that is larger cannot be sucked easily into filter foam. The result is too much larger stuff will simply get sucked onto the surface of the foam and work to clog it since it may ne be getting broken into smaller particle sizes.
This was impressed on me some years ago when I began using the very large fofoam Matten filters in pleco breeding and grow tanks. I do not light them in the usual fashion. natural light and room light when they are on is what I have, The results is most such tanks have no bacground the glass is clear. I had posted pics of one or two of the pleco tanks. One of the resplies asked me how I managed to have such clear water. You could clearly see the indentation in wh white painted cimder block wall behind the tank. So I did an experiment.
I taped a quarter to the outside of the back glass and discovered i could read the dat on it through the fromnt glass. Since 100% of the filtration was foam. This oproved to me that the foam had to be doing mechanical as well as hosting the biological filtration my microorganisms.
The bast par of this I is then loaded my 3rd canister 100% with Poret foam media. I had to include the top floss sheet as it was needed to make everything connect to the pump on top as the original design incorporated. But that floss was the final media before the water returned to the tank and was u Under an inch in thickness, Below it the water passed though about 7 inches of 20 ppi Poret foam half of which was in each of the two media baskets. The water came up through the baskets before it went through the floss.
When I asked Dr. Tanner how I would now whenn I should rinse the media in that canister, he said when I noticed the return had slowed. My other two non Poret canisters I clean every June and December. I have had Poret loaded canister for at least 7-10 years. I just did my second clean about 2 months ago. I will confess that I let it run more slowly for several months before I did that clean. But the tank also has an AquaClear 300 (aka 70) running and is loaded with Poret as well but I rinse that media weekly for the most part and the tank is a heavily planted 75 gal.
Some of my Matten folters have been running for years without ever being cleaned. When I asked Dr. tanner as I was setting thes up how would I know when they should be cleaned, he said, "When the warer level behind the foam was clearly lower than the the level in the reast of the tank, it was time." Most of the Iattens I have cleaned came off of the tanks I have shut down over the past 3 years as I downsized from 20 to 29 to a max. of 12.
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Back in the fold
If you want to see smaller fish holding their place in faster water, have a look at this vid. I know it from my days of keeping Altum angels. I started the vid wher you can see the flow and in the earlier part before the altums are featured you will see the small fish in the decent current. Feel free to kwwp watching the rest of the vid as it is pretty neat.
