On my 30G tank I have pressurized C02 (10lb) setup along with a Fluval 304 for filtration. Nether of these are overkill for this tank, works out very well.
I got the C02 cylinder from a local restaurant supply store and bought my regulator from our sponsor AquaBuys
. I bought a clippard needle valve off of another member of this forum. The filter I bought from Big Als.