Ok so got a 46 bow with canister filter which I know is not the best. But I have a 20 gal laying around as well what I was thinking is that maybe I can use the canister as a prefilter and turn the 20 gal into a sump with frag rack. So the canister will be filled with cotton and pour into the sump pass live rock and push back up to the tank. Good idea? Figured it would be a great filter