You will have high ph with the sponge. It is inferior to a good canister. You are more apt to have algae problems than with a canister filter.
If you have lots of plants you will be asking for trouble because of CO2 out gassing. It will do little or nothing at reducing DOC's from the water.
If you do lots of breeding & water changes it could be fine with livestock mostly set ups.
Thanks Hardstuff, Yeah my ph is around 7.6-7.8 according to the tests.
AND I've been having algae problems. First, some mucus looking stuff that clouded the tank and covered all the glass (since gone), then green spot algae on the glass, and some clouding issues.
I'm using liquid Excel right now instead of CO2 gas. Will the sponge filter still dissipate it?