Bettas, also known as Siamese fighting fish, are a beautiful, vibrant addition for any aquarium enthusiast. However, these small fish are extremely territorial and will fight to the death if provoked. Keeping a close eye on your bettas is essential for the health and safety of your entire tank.
Choose Your Gender
Bettas aren’t known as "fighting fish" for no reason; they will nip, pick and bite other fish into exhaustion and even death. Males are much more aggressive than females, often fighting to establish territory and pick a prime mating spot. Females are smaller and more passive, and tend to get along well with other bettas. Pairing two male bettas in a small tank is never recommended, although a male and a female may coexist if the tank is big enough and there are plenty of places to hide. Female bettas often live together without issue, but they must be observed carefully in the hours after introduction. If you do house a male and a female together, make sure to separate them if they mate; if you don't, he may kill her in order to protect the eggs.
Try Different Fish
If your bettas aren’t happy with each other and you have an established community tank, put one betta in with the other fish. Bettas generally get along fine with other non-aggressive fish, as long as none of them are fin-nippers. Place a small breeder box inside the large aquarium and place the betta inside the box. Allow him to acclimate to the new tank for an hour, and then turn him loose. The other fish may chase and pick at him a little while they establish order, but this will die down after a day or two. Remove the betta if he appears injured or is overly aggressive with the other fish.
Divide the Tank
Drop a plastic divider in your tank if you need to house multiple aggressive bettas. These thin plastic sheets fit snugly at the bottom and sides of the tank and allow water to travel through while preventing the fish from attacking one another. Slide the divider into the tank, pressing it firmly into the gravel. Place plants and decorations on each side of the divider and place one fish on each side. While the fish will flare and display to each other through the divider, they will be safe on their respective sides of the tank.
Separate tanks are the only viable solution for extremely aggressive bettas. Prepare an individual tank of at least one gallon's capacity for each fish, adding plants and gravel to the tank to give the fish some cover. The gravel in small tanks provides adequate filtration, so no filter is needed in tanks under five gallons. Add a small, gentle filter and heater to larger tanks to keep the temperature between 72 and 82 degrees Fahrenheit. Introduce the fish to their new tanks slowly to prevent shock.