Fish like all animals can be aggressive. Aggression amongst fish can be displayed by fish nipping each other’s fins and biting each other around the mouth and eyes. Fish stressed out from aggression can refuse to eat which leads to starvation. Sometimes aggressive fish can outright kill their tank mates. In this article, we will discuss the causes of fish aggression and several techniques on how to prevent this type of behavior and maintain a peaceful home aquarium.

To understand a problem, you often look at the cause. Fish aggression can usually be related to three different causes.
The first cause is territory. Fish like all animals are territorial and each fish has its designated spot in the tank or bowl. The introduction of new fish to you tank can inspire the need for your older fish to defend their territory.
The second most common reason for fish aggression can be attributed to male-female ratio in your aquarium. A tank with a few females and many males can create a lot of tension amongst the males as they attempt to mate with the females in the tank.
The third most common cause of fish aggression is hierarchy. One fish has become the alpha of the tank and there is a beta that wants his role. Fighting amongst the fish can easily lead spiral out of control and stress other fish in the tank.
Now that we know the why. How can we prevent this fish aggression?
To solve the first problem experts suggest before introducing a new fish rearrange all the decorations in the tank. You can do this during a weekly tank cleaning. This disorients the fish regarding established territory. In addition, a new fish can be introduced into a tank while the lights are off in the tank and when all the fish are asleep. The fish will adjust to their new roommates.
In terms of the imbalance in the gender ratio of your fish. Experts suggest maintaining a balance in the ratio of male to female ratio in tank. Another option is to have an all-male or all-female tank. All options reduce the amount of aggression in the tank.
Finally, in terms of hierarchy, have a slightly bigger fish or a small school of fish to tank can prevent fish from intimidating other fish in your tank.
Also know what type of fish you have in your tank. Are the fish in your home aquarium passive or aggressive? If you have aggressive fish add aggressive fish to your tank. If you have passive fish add passive fish to your tank.
So, you have done the preventative measures, but you still have a problem fish or several problem fish in your tank.
Expert say to take the problem fish and put them in a breeder box tank for a few hours to a few days. The time away from their home environment gives the fish time to change their behavior.
If this behavior continues you will have to take the fish out of the environment. You can give a fish to another person or take it back to the pet store where you originally bought the fish.
In closing, fish like all beings can be aggressive. Being able to manage that aggression is a part of aquatic pet ownership. Remember the major reasons for fish aggression are over gender ratio, territory, and hierarchy. Preventative measures can be taken to limit the aggression. If these preventative measures do not work, you can always remove the fish from the tank.