Hmm cichlids are very aggressive- some more than others. Did the place you purchased them from tell you they were incompatible? If not, that was mighty irresponsible of them. If so, I dont know that I would have bought them knowing this unless I could house them separately. Usually, when you go to pet stores, and you see many different tanks with cichlids, the reason they are not mixed is exactly as you have been told, incompatible. The only suggestion I have at this point, you need a HUGE tank, and plenty of places for the less aggressive ones to hide from the others. They may settle down eventually, but dont be surprised if you find a few dead ones. I love cichlids, but this is why I dont keep them, cant have all the species I like together and no space for that many tanks.