I just purchased a 75 gal. salt water aquarium with a 30 gal. sump. Everything was horribly dirty. Tank was up and running for 2 1/2 years and never cleaned. I took everything apart and cleaned it so now to the questions. The sump has I guess bio balls in it. The filter side has 3 levels, bio balls, and something that looks like shredded plastic and on top of all it has what looks like a foam cover. What would be the best media to use in this sump. I am going to try to upload a few pictures so maybe someone can give me some input on this sump and what to do to make any improvements. Also, one more stupid question. . . . where would I put the heater in the sump ? It has 4 sections. The filtering, skimmer, a shallow empy, pump back to aquarium.