Injuries caused by aggression can lead to life-threatening bacterial, fungal and parasitic diseases in your fish. You can solve this frequent cause of death by taking steps to correct the incompatibility problem. The solution usually requires physically separating the aggressive and submissive fishes. To reduce aggression, provide plenty of structure in your aquarium in the form of rocks, corals, plants and driftwood. These items can provide life-saving refuge for your smaller and more submissive pet fishes.
For more information, please read the story Aggression in the Tank.