Cichlid aggression prevention is a very important topic when it comes to these tropical freshwater fish. If certain cichlids are allowed to be bullies in the tank this can cause undo stress on the other fish and may cause a rise in disease and death. That would not be good! So probably the best way to avoid conflict between your fish is to make sure that you have lots of cichlids in the aquarium. It seems like a strange concept but if you put in a lot of cichlids they won't have enough space to establish territories and the result can be peace in the tank with less aggression. Believe it or not, this concept works! if you do this approach please be sure to have enough filtration.
Within the African cichlids natural habitat, they are aggressive by nature and it is not uncommon to see them chasing each other around. Or you may see them peck at each other's fins or may appear to be fighting face to face. This is their normal action and behavior but if you notice that a single fish is constantly being picked on, then you will want to pay close attention. The peace of the tank can disappear quickly and the fish could get sick or die and sadly this can easily spread sickness and death throughout your aquarium.
Here is some advice to help you prevent cichlid aggression if this type of behavior becomes apparent in your tank:
If a particular cichlid keeps chasing other fish away from a particular area this is a good sign that it has established a territory to protect. You can eliminate this aggression by re-arranging the decorations in your tank, thus taking away the bullies area, which levels the playing field again.
If it continues to happen, it's a good possibility that you may need to add some more fish because obviously there is enough space to establish territories. Never just add the fish and walk away. Cichlids are very smart fish and they will immediately begin to pick on the newbie. Add your fish when you do a water change and when you change the water, move the decorations around. By the time the stress of the water change wears off, they probably won't even notice that other fish have entered the tank. Hopefully this will reduce the size of the territories and re-establish peace in your aquarium.
If aggression is coming because a particular cichlid is smaller is size than the others, remove the smaller fish and put it into another tank for awhile, for example in a hospital tank with lighting and a filter. Feed the smaller fish 3 times a day and feed the main show tank fish 2 times a day. In time, the smaller fish will grow bigger. When the smaller fish has grown in size, then do a water change, move the decorations again and add the fish back into the tank. Aggression will be alleviated.
You can do the same thing if there is one particular cichlid that is bigger than all the others, or if he is more dominate than normal. Remove him for a day, don't feed him, and then re-introduce him into the tank. Keep him in another tank or bowl for only a day. You don't need lights or a filter, just keep him out of the main tank for 24 hours (but not longer than that!). Don't do a water change and don't change the decorations. While the aggressor is out of the main tank, the other fish or fishes that were being picked on, may establish their own little territories. And when you add back the former bully he will now be the 'newbie'. Hopefully this takes care of the problem. If the bully is very big though or very aggressive it may not work. If that is the case, then you may need to give the smaller fish away or give away the aggressor. Try and experiment with different things first, but if all else fails then you may have to permanently remove one of them.
Each fish has it's own personality and each fish keeper has their own opinion or way of doing things. The important thing is to keep peace in the tank and if that peace is disrupted, experiment to see what works the best