I have a male cherry barb who is a bully. During the day time (lights on), he runs one side of the tank. I've noticed he is the only fish that actively chases and is aggressive with everyone else. I'm pretty sure a couple of my females have torn fins from him, and now I have a pristella tetra with red marks on it. What should I do about this guy? I'd hate to separate him. The tank is moderately planted. I have 5 cherry barbs, and 6 pristella tetras. I have another 6 cherry barbs coming and 6 more pristellas. I'm hoping that lessens the aggression and stress.