I'm planning on running an algae scrubber as the sole filtration on my 20g tank. No other filter media at all, no sponges, no filter floss, no phosphate or nitrate removal media and very little carbon occasionally. I'm going to be feeding live enriched brine shrimp, culturing my own phytoplankton, rotifers and copepods. I don't know if I really want to have fish in my system or not yet. I'm just considering inverts and coral. MAYBE small clownfish for my wife's sake. lol!