well my tank has a filter built into the back. Right now I only have 1 clown (1 of my clowns died the other night, i couldnt get him to eat), 1 sixline wrasse, 1 cleaner shrimp, 3 hermet crabs, 1 scarlet (hitchhiker), and 4 nass snails. As for coral, i have frogspawn, GSP, trumpet coral, some zoos, and a leather finger.