My current stock in my 150g cichlid tank
10" male jack dempsey
6-7" female jack dempsey
7" male red devil
5-6" female red devil
2x 4" male pink convicts
5-6" female green terror
3" female texas cichlid
8" polleni
3-4" pair on firemouths
3-4" pair of convicts(with fry)
Although there is some aggression in this tank, the only real problem is the convicts and that will be solved, once the fry is removed. It is trail and error, you could do this same stocking with other fish and have complete turmoil.