Wow, that is a lot to grasp. I have recently added to a cichlid tank. The tank initially had the Jack Dempsey in it, about 6" or so. I added a few smaller fish, oscar, parrothead hybrid, and two gouramies. I moved around the decor in the tank and created more hiding places for the smaller fish and so far the big guy has left them all alone. I have even noticed the oscar and jack dempsey cuddling. I am not sure of the origin of any of these fish, but all seems peaceful thus far.