As stated above
we have to separate mechanical and bio-filtration in both our minds and our words
Nothing is more important than gph
for mechanical filtration
yet for bio filtration gph is a minimal impact
I personally feel that bio-filtration is one of the best industry hypes that the aquarium trade has produced. I have several tanks that are running off of an AC HOB with one sponge and no rings
no other bio-media what so ever
and they have zero ammonia and zero nitrites 100% of the time
It is completely true and valid that with nicely modified bio-filtration, the bacteria colony can increase much (much, much) faster to accommodate an increase of bio-load (I.e. adding fish)
But without such bio-filtration bacteria will still form throughout the tank/filters and do everything that they will do in fancy bio-media set ups.
Based on the above understanding, I feel that bio-media is a nice safety net to have in place, but is far from necessary.
I personally like for my filtration to handle the bulk of the waste that accumulates in the tank. Therefore I use high flow rates to push the waste to the filters intake.
One can very validly argue that this is also unnecessary as the owner can easily remove the waste during regularly scheduled maintenance. I could not argue that point at all
In the end
enough water movement to prevent stagnation and to promote oxygenation is necessary
beyond that there are a lot of paths to take in improving filtration to account for other things
such as nurturing a bacteria colony or removing waste
This is the philosophy Ive come up with after screwing things up for man years
and finally finding a method that works for me
I wish you the best of luck finding an approach/philosophy that works for you
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