Okay, so I have the day off for school due to the massive amounts of snow dropped on the piedmont of NC...aboud 1.5 inches so far....but as I was sitting here I was thinking about possibly changing the filtration on my 55 gal discus tank....as of now I currently have 1-XP2 Canister and 1-Hydra-Sponge Filter rated for a 180gal tank. I have been having some problems keeping the water level in my 30gal (36 inch tank, not that it matters in this case) heavily planted tank up so that the HOB filters dont diffuse the CO2 injection that is currently on there. Now to the question....how much trouble would I run into putting another Hydra-sponge (also rated at 180gal) and moving my XP2 to myh 30 gal and doing away w/ my HOB filters? I have heard many stories about people only running sponge filters in their discus tanks...currently I'm doing 2x 50-75% w/cs weekly on my discus tank. It is bare bottom with lots of driftwood. I was thinking about running the XP2 on the tank a few weeks while the new sponge's bacteria grew. Would this be a beneficial idea for both tanks or should i leave it be?