I wasn't sure what you meant by "fogging up," but have you tried a different filter? My tank would get scum on the surface very quickly so I bought a TOM internal mini filter ($12 or $14 at petsmart.) It cleared it right up. It says it can control up to 5 gals, so what if you saved up and got 2? you could put one on each side, and that might help keep you tank much cleaner.
*edit* didn't realize you said you have THREE boys, but what if you still got 2 TOM's and put on on each end of the tank? it should still do the trick, plus they're extremly quiet filters.