So I have a 180g tank that is running with a 40g sump and an FX5. The stock is (2) 7in Oscars, (2) Nicaraguan, (2) Jack Dempsies, (1) Firemouth, (1) Green Terror, and (5) Silver dollars. All the fish but the O's are still juvies so I have some time (and a 75g waiting to be filled)... But I am torn between getting another FX5 or 2 smaller canister filters for more mechanical filtrarion.