depends on the size of the fish, temperament, and amount of hiding places for them. I normally buy two or three fish at a time and slowly add them until it looks well stocked but not over stocked each time rearranging the aquarium so new ones don't get picked on. If you want exact numbers I would say 2" fish per one gallon so probably 27-30 inches of fish which should be about 10 very small cichlids, or 5 larger cichlids. I might be wrong so if anyone wants to back me up...