Originally Posted by Nubster
Is there a point that one can actually go filterless? Just a powerhead for water movement and to disturb the surface for oxygen exchange?
With sufficient live plants, an aquarium does not "require" a filter. Minimal water circulation is advantageous (not everyone agrees on this) but a powerhead might be too much in smaller tanks. The optimal word is "minimal" water movement, so valuable CO2 is not needlessly driven off.
I had a 10g tank well planted, no filter, no light (sat in a bright west-facing window), just the heater. This ran for several months with fish and snails and did very well. It was an experiment. I found that the fish and plants were fine, but the water was not crystal
clear, so in the end I added a small sponge filter just to circulate the water and provide removal of suspended particulate matter.
Which brings me to the issue of filter-less planted tanks. The filter in a planted tank only serves two purposes, those mentioned in the preceeding paragraph. It is not there to do any cleaning of the water, that is the job of the plants; nor for biological filtration, as that too is better handled by plants.