what kind of sponge.preassembled air driven(the kind in the plastic case) or rinseable air driven.basicly if you are just using your 2 gal. as a betta home ugf is fine so long as the suface agitation isn't bothering the betta.ok now i see you sig,so yea ugf is fine.despite the limitations i also like the plastic cased sponges except i wish they didn't have the carbon in them.