Well, it is not.
Originally Posted by stevenjohn21
I just feel that a higher flow rate going through as much media as you can manage to put in the filter would be better all round .
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And please don't take that offensively, it is just that this is another of those "myths" that are out there.
With respect, you don't seem to understand fully the tasks that a filter manage. First, there is a big difference between cleaning the water and clearing the water. Mechanical filtration--moving water through any media, esp the wool pads/sponge/floss--is clearing the water by removing suspended particulate matter. I don't have statistics but I think it is highly debatable how effective more of this can possibly be in any tank. And as someone mentioned, the faster the water goes through this media, the less effective the capturing of the particles will be.
Then we come to the "clean" aspect. This can be biological and chemical. Nothing, and I repeat nothing, does this better than live plants. Now, you need it balanced to be 100% effective, and most of us have more fish in a tank than what will allow this, so the filter equipment gives us some leeway. But again, there is only so much the filter can do.
With respect to biological filtration, involving the nitrification bacteria, there is more of this going on in the substrate and on other hard surfaces than in any filter. And the bacteria will only exist at the level necessary to handle the ammonia/nitrite--no more, no less. So again with the fish load balanced for the tank, there cannot possibly be any advantage to more filters, biologically. And the fact that in well planted tanks biological filtration is detrimental to plant growth anyway and we do not want to encourage it, that is another negative.
The denitrifying and anaerobic bacteria can be forced to increase by too much filtration, provided organics are present to sustain them, and this is not beneficial.
So that brings us to the chemical filtration, using carbon or other substances to alter the water chemistry. This has advantages in non-planted tanks, but is highly detrimental with live plants. And again, the plants can do this task better, so why not let them get on with it?
You can read more on some of these points here:
The bottom line in all this is that there is only so much filtration that can benefit any aquarium. And exceeding this can actually be more detrimental.