My comments on issues raised in the last two/three posts.
Filtration is not always well understood in this hobby. AbbeysDad is correct in what he posted. Let us begin by deciding what "filtration" in the aquarium actually involves.
First, it moves the water around, so the water flow or current must be considered. Most of the hobby fish do prefer less current. Fish that spend six months of the year in flooded forest are not being exposed to strong currents. Some fish do need them, as they live in flowing streams. This is why knowing the habitat of every species we intend to keep is important; we need to ensure we are providing the basic needs for that species, and water current is a vital part.
An example. One of my tanks is a 40g, surface dimensions 36 by 18 inches. I have a dual sponge filter in the right rear corner. There is very,. very little water movement. The 40+ fish in this tank are in a basically ideal environment.
Nannostomus eques, Parachierodon simulans, Hyphessobrycon amandae, Characidium fasciatum. All residents of quiet blackwater streams, pools and flooded forest
Aside from that, what do we expect the filter to achieve? Basically, nitrification. We want
Nitrosomonas bacteria to grab the ammonia, and we want
Nitrospira bacteria to grab the resulting nitrite. Provided the filter is sufficient for the tank volume and fish species/numbers, this will be achieved. We now know that if the water movement through the filter is too fast, the bacteria cannot function well, or even at all. "More" is not beneficial, and may be quite the reverse. This applies not only to the flow rate, but the filter size and number of filters too. There is only so much the bacteria can do, and this is basically not relevant to the filter(s).
We must also keep in mind that the substrate is far more important when it comes to a healthy aquarium than any filter. More bacteria species live in the substrate, and the "filtration" they achieve is much more important to a healthy aquarium.
We can have a well-balanced and healthy aquarium with no filter at all (meaning no "filter" equipment). All of my tanks have a filter, but it is much less than any of the common "recommendations." Too many have the thinking that they can somehow overload the system with more filters, but that does not work.
I follow the EI method for fertilizing my plants, so I do large water changes and have very well planted tanks. Along with the high gph rates.
I would suggest there are two problems here, for fish. One is the flow rate which may be detrimental (not knowing the species, I only make the observation it may be). But second, the EI method is not good for fish, as I will explain. But keep in mind that most planted tank aquarists that are into things like mega light, diffused CO2 and EI fertilization have tanks with few or no fish. As soon as you have fish tanks that happen to have plants, the emphasis must be on the fish if we want to provide a healthy environment for the fish.
Every substance added to the water in the aquarium gets inside the fish. Water is continually passing through every cell via osmosis, entering the bloodstream and internal organs. Substances also enter the bloodstream via the gills during respiration. The ideal is to add nothing at all to the water, but when additives are needed, use no more than absolutely necessary. Water conditioner for example does not need to be over-used, because it does impact the fish. Same for all these plant additives. I went into this in detail with a couple of professional biologists and microbiologists a couple years back when dealing with an issue in one tank. Fish do not need to drop dead to prove these additives are impacting them, they are simply weakened and this means more issues down the road.
