My 150 show tank has a mixture of everything. I have two fronts, Yellow Labs, Zebras, Peacocks, Flamebacks, Haplocromines, you name it. Fish are just like other animals. Just because they may have a nasty reputation dosen't mean all of them will have a nasty attitude. If you are worried about aggression then Cichlids in general are probably not good for you. It's trial and error. The more cichlids in a tank the less aggressive they tend to be.