not necessarily. I have 10 africans in my 20 right now (5 jewel fry and 5 mixed africans). The 'over populating' and the fact that they're all less than 1/2 an inch stunts them and forces down the aggressiveness. (They'll go into my spare 55 gal within a year though). Most of the fish he had grow to their environment. It was inevitable that the cichlids would feel cramped, kill weaker species, grow to accommodate new space and so on.