I think I know the answer to this question, but I'm going to throw it out here anyway.
I've got a 15 gallon tank with a aquaclear 20 gallon filter. I've got 13 fish in there already (6 x pristilla tetra's, 1 x male betta, 2 x black mollies, and 4 x peppered cory catfish).
According to the aq...