Will Betta Fish Kill Each Other in the Same Tank?

Betta fish are also called Siamese Fighting fish. Despite their dainty and beautiful fins, Bettas are highly aggressive.

Pet stores often tell new Betta fish owners to be careful because they will kill any other fish in the tank. Their bloodthirsty ways, however, are not entirely truthful.

Betta fish are aggressive and kill other fish in some cases. That said, it is unlikely that a Betta will kill another Betta fish when the tank conditions are right. 

Continue reading for everything you need to know about housing Betta fish, what makes Betta fish aggressive, how to stop Betta fish from fighting, and more.

Will Betta Fish Kill Each Other?

Betta fish are territorial and get aggressive. So, will Betta fish kill each other if they are in the same tank? In short, no, but they will bite one another and chase each other around. Betta fish have teeth, so nips and bites from Betta fish cause wounds and fin tears in other fish.

Two male betta fish housed in the same tank, especially if it is too small a tank, will fight to the death. It is unlikely that a male Betta fish will kill a female fish or fish of a similar size, but fights and chases are common.

Betta fish are known to eat baby fish or fry. Betta fish also eat eggs laid by females. This egg feast from other fish makes male betta fish particularly aggressive during mating season.

Blue and Orange Betta

Why Are Betta Fish Called Siamese Fighting Fish?

Betta fish are also known as Siamese fighting fish because they originate from Thailand in the Mekong and Chao Phraya rivers. Siamese directly translates to a native of Siam (Thailand).

Siamese fighting fish is a decorative fish species that are extremely territorial, especially during feeding and mating times. In the wild and captivity, Betta fish will bite, chase, attack, and in some cases kill one another giving them the name of a fighting fish.

What Makes Betta Fish Aggressive?

Like all animals, Betta fish have different temperaments which will affect their levels of aggression.

Keep in mind that certain tank conditions contribute to Betta fish being more aggressive.

Betta fish get aggressive for three main reasons:

  • Tank Size
  • Food
  • Mating

Tank Size

Betta fish are territorial so a small tank with two Betta fish will cause them to fight one another over dominance of the territory.

One Betta fish needs a tank with a minimum of three to five gallons. If you plan to house two Betta fish together you will need a tank with a minimum of 10 to 20 gallons per Betta fish so that each has its own space within the tank.

Male betta fish are more aggressive than female Bettas, so it is easier to house multiple females together in a tank than multiple males.

Betta sororities are tanks with at least four to five female Betta fish. Sororities should be housed in a 20-gallon tank at a minimum.


Betta fish are known to be aggressive during feeding times. If you keep other fish in the tank with Bettas you might notice that the Betta fish hog food by using physical aggression to get at pellets, flakes, or wafers.

Mating Season

You will know it is the mating season when male Betta fish begin making bubble nests at the surface of the tank. Females release their eggs and males collect them in their mouths and spit them into the bubbles.

During this time, other Betta fish are likely to eat the eggs inside of the bubbles. Male Betta fish will defend their bubble nests.

Once a female lays her eggs it is recommended to take the female out of the tank and place her in a separate tank until the male becomes less aggressive as he may kill her for eating the eggs.

Is It Bad for Betta Fish to Fight?

It is not a good idea to let Betta fish fight. Fighting between Betta fish can increase stress levels and cause wounds. You want your fish to be happy for them to live their longest and best life.

The chase heightens stress levels which can have adverse effects on your fish. Bites and wounds from fights can lead to fin rot or infection.

How to Stop Betta Fish From Fighting

Getting Betta fish to stop fighting takes preparation and time. First, you want to increase your tank size to at least 10 or 20 gallons so that the fish do not intrude on each other’s territory.

If you do not have the space for a bigger tank, separate your betta fish into two tanks. Ensure each smaller tank is a minimum of three gallons.

When introducing fish to each other, use a barrier to allow the fish to see each other without being able to hurt one another. Try keeping one fish in a clear plastic bag and inserting it into the other Betta fish’s tank.

During feeding time, use a variety of fish food sized for each specific type housed in your tank. This will ensure that little fish can get to their food and eat it quickly before another fish has the chance to steal it.

Place fish food in varying spots of the fish tank to spread out where fish congregate to feed. This will help your Betta fish feel that its territory is not being intruded on.

What Fish Can You Keep In a Tank With Betta Fish?

Betta fish have aggressive tendencies but in the right conditions, they can be housed with other fish without fear of carnage.

Here are some of the best fish to keep in a tank with a Betta:

  • Neon, Cardinal, or Rummynose Tetras
  • Ottocynclis
  • Kuhli Loaches
  • Platies
  • Mollies
  • Bristlenose Plecos
  • Snails

Wrapping Up

Betta fish are aggressive fish and are known to fight, chase, and sometimes kill other fish. Luckily, there are ways that you can house fish of varying species and other Betta fish with Siamese Fighting Fish without harming them.

These iridescent fish are a blast to own and watch their delicate fins swim around a tank. As long as they have enough space and have time to adjust to one another’s presence, Betta fish can have other fish living with them in peace.