They are quite variable in their behaviour and personality. When young, they are always on the move and very competitive for food, always jockeying for advantageous position. When they become sexually mature, they can become quite rough on one another, until a compatible pair forms. Then that pair will not tolerate conspecifics. They will continue to have a solid pair bond if they are kept in with a few target fish that can take care of themselves (heterospecifics). I have had breeding pairs mixed with other similarly sized Parrots and had to remove these "extras" to avoid a thrashing. I kept one pair in a 180G all by themselves for a year and they were so calm and laid back that I decided to add a full sized pair of Chocolate cichlids, a pair of Heros Severus and six large Geophagus altifrons. Everything was amazingly peaceful ... for one day then all h--l broke loose, with the male terrorizing the newcomers to the point of threatening their lives. So take it for what it's worth. You never really can tell what's going to happen. They can be very variable in mood and temperament and it can change quickly. Having said what I have, don't misinterpret me. I really like keeping them. They are truly a magnificent SA cichlid.