What to Do About Bully Fish in an Aquarium?

Each fish is an individual, although species do tend to display certain predictable behaviors. To avoid one fish eating another or one fish chasing all of the other fish about, the aquarium owner needs to choose species known to be peaceful. But still, fish may become aggressive to smaller fish or to others of their kind when it is time to spawn.

  1. Check Species

    • Although fish sellers will try to be honest about what fish are peaceful and which are aggressive, they don't always get it right. Some species such as the plecostomus and the red-tailed shark will be peaceful when they are juveniles, but when they grow to be a few inches long, they become more aggressive, even to members of their own species. According to "Freshwater Aquarium Problem Solver," species such as barbs will chase and eat the fins of any long-finned fish such as a fancy guppy or a male betta.

    Spawning

    • The spawning behavior of many species of fish involves the male chasing the female wildly about the tank. Some species, such as cichlids, will then lock their mouths together and seem to wrestle. Any other fish in the tank of other species may become the targets of the spawning pair's actions. Thick aquarium plants---live or plastic---can act as hiding places for the harassed fish as well as aquarium safe tubes and shells. The spawning behavior passes away on its own.

    Hiding Places

    • According to "Tropical Fishlopaedia," any décor that acts as hiding places for harassed fish needs to have rounded edges so a fish being chased can't hurt itself swimming into it. Shells need to be replaced as soon as their color begins to fade. Large aquarium safe rocks with small holes in the center are often ideal and attractive hiding places for small fish. Small earthenware pots make a nice cave. Adding a small mirror can help distract the aggressive fish. It will attack the mirror and not the other fish.

    Feeding Strategy

    • Some fish will become aggressive if they see all of the other fish getting fed. They chase away the other fish to get at the food. This can be countered by feeding at two places at once simultaneously. Be sure the top-feeders get floating food at the same time than bottom feeders get sinking food. This may help bring some peace to the tank.