The reason for the increased waterchanges that Dino and S-flower recommended is because fish secrete a group of hormones that inhibit growth. That is a natural evasion so that the large group in the wild doesn't out grow their area, but in the fish tanks if properly housed they can each grow to full size and be fine. (This is not an excuse not to do waterchanges to prevent growth, both the rise in nitrates and the inhibited growth will kill your fish if you do that.)
So increased waterchanges keep those hormones to a minimal.
