Fish like cichlids are highly intelligent fish. You absolutely will find this one is friends with that one, and this one hates that one, and then this one has a house that that one is not allowed in and then this one is the boss that nobody messes with while this is the little wimp that nobody likes. There is so much personality going on amongst the fish, and the thing you need to be looking for is the boss. There is always going be a boss. He is usually a very big, very colorful male who is usually controlling the middle of the aquarium and his job is to keep all the other fish in line, because, in the aquarium, he is the boss. There is the second boss, the third boss, all the way down to the biggest wimp –and they all know where they fit in. This is the set hierarchy in the aquarium.

A good boss swims around nice and proud. A good boss will give the other fish a push here and a push there, but doesn’t really hurt anybody. A bad boss picks on a certain fish and just will keep picking on him until he pretty much wears him down and possibly kills him. This is normally very visible activity that you can see in your aquarium. The other thing a good boss will do is break up fights, because he likes the hierarchy the way it is and he doesn’t want anyone changing it.

This is why you can often see a very well-established aquarium, where a very little electric-yellow is chasing around the big Venustus (and that usually would not make sense, but it is the little brother syndrome). Big brother sees little brother as dominant while they are growing up, so when they are older this didn’t change. The electric-yellow was dominant and the Venustus never figured out that he has grown bigger and stronger. He is still scared of the electric yellow that is now a little fish compared to him.

This often happens if you have a good boss, but on the other hand if you have an "Adolf Hitler" running your "country" so to speak, you are in trouble. When you see one fish running around beating the hell out of the other fish, do not be that guy that walks into the aquarium shop in a really bad mood with the fish in his hand, shaking the fish in the bag. When asked what’s wrong he says “this fish killed the rest of my fish." Then he is asked “Over what period of time?" He says, "It killed all my fish over the last year." So why didn’t you think about that after he killed the second fish? You can’t actually control your aquarium? Do you have control over it?"

If you see one fish beating up all the rest of the fish, you have two options. Option Number One: Get more fish as this will disperse the aggression or Option Number Two: get a bigger fish to dominate the aggressive one. For cichlids, make sure you have enough fish to disperse any aggression and also make sure you have a good boss. If you don’t have a good boss, you need to get more fish. Just bring him down to the shop, preferably after he has killed the first or second fish, not after he has killed 20 or so.

As per.com Paul Talbot
Taken from www.cichlidhub.com