Well I just added another filter an xp3 so the filtration is good enough for a 420g. The fish will like that. I combined the little pellets in a ehiem with pot scrubbers, filter floss, the white block and cylinderical things (Its been 5 years I know I should know what its called), crushed coral, and losts more filter floss. The filter is jammed packed and the flow is insane.