I have a 75 gallon south American cichlid tank, with a gold severum a oscar a fire mouth and 4 black convicts. I was debating on if I need a powerhead in the tank, I have a fluval 406 canister filter and a marineland 350 hang on the back filter also I have a air pump on the tank. Do I need a powerhead? Does the fish I have require a powerhead? Will the powerhead be beneficial to my tank? And if I need one how many would I need for a 75 gallon and what gph?