I was always wondering this, can sponge filters be your only means of filtration and be it's only source of filtration? I'm wondering this because i may need more room and i have my buddies 50g tank here with a heater but no filters but i do have two sponge filters a large hydor v and a medium one with two air pumps ones rated for 100g and ones rated for 80g. And i could possibly get more and each pump has two ports so thats potentially 4 sponge filters now will this be enough? i have two stocks that could go in, either two p bass in the 50 or they could go in my 29g for a tad before they get bigger. or my stock thats in the 29 which is two small festae tire track eel proteus pike and 4 cory cats. Would the sponge filters be able to support for either stock? yes the tanks are GROW OUTS, i know the potential sizes of all the fish. Thanks