I have a 55 gallon tank. Currently there are 2 blue acara, 1 tiger oscar, 1 green terror, 1 fire mouth, and a clown knife. I've never had cichlids before, other than the tiger oscar. All the fish are roughly the same size, about 2 to 3 inches. The fire mouth fire mouth is probably the biggest in the tank at 3 inches next to the knife. He seems to be very aggressive. He chases the acara and the terror around the tank. The oscar pretty much keeps to himself but occasionally will fight with an acara. The terror doesn't bother any of them. And the knife hides in a large piece of driftwood until feeding time. I understand how big these fish get and my tank will be too small once they mature. I plan on trading in the oscar and knife when they get bigger. My question is more about what to do with the fire mouth constantly chasing everything. There are multiple places to hide in the tank with live plants, large driftwood centerpiece, and a rock grotto. He finds them all. Any idea's? Also what else would be compatible with these fish when I replace the oscar and knife?