One quick thing about the sponges: You should never need to replace them.
I've had the ones in my fluval 304 for 8 years. When you want to clean them, get a plastic bag (I use a 2 gallon zip-lock), add a couple cups of tank water (yes tank, not tap), and put the sponges in there. Roll the open end of the bag down securely, and shake vigorously. use the dark brown water to water house plants (full of nutrients), and repeat.
I never rinsed the sponges under faucet water because my water had a lot of chlorine, and I wanted to keep as much of the bacteria on the sponges as possible.
Aquarium: 55 gallon with 60 lbs fluorite 20 lbs gravel
Filtration: Eheim 2026 Pimp #168 with Fluval surface skimmer
130 watts of 6700k PCs 12hours, 130 watts 10K 4 hours.
Co2 suppl.: 10lb tank with Milwaukee al in one.
Flora:Java Moss, Water Sprite, Microsword, Anacharis, Water Primrose, Rotala rotundifolia, Cryptocoryne wendtii, Echinodorus x barthii, Bacopa monnieri
Fauna: 3 Sailfin Mollies, 8 Tiger barbs, 6 Cory Julii, 6 Ottos, 2 SAEs, 9 Amano shrimp.