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How and Why Do Betta Fish Fight?

Betta Fish are legendary in the aquarium world. Males are known for their bad attitudes and fights that can last until one or both fish dies.

There’s a persistent myth that male Bettas will also chase and kill other aquarium fish, which we’ll look at in a little bit.

But first, let’s explore how and why of Betta Fish fight.

A Bit of Betta History

Betta Fish are also known as Siamese Fighting Fish. Bettas (Betta splendens) hail from the Mekong River Basin, which covers a significant portion of Southeast Asia.

They were first raised in Thailand, then known as Siam and were popularized over 150 years ago when children began collecting Bettas to watch them fight. Betta Fish are known in Thailand as “pla kat,” or “biting fish.”

Eventually Betta Fish became popular enough that people began breeding them for color, finnage, and willingness to fight. Wild Bettas are drab, with hints of red and blue in males.

They have short fins and are still aggressive, however their bouts last for a few minutes at most.

Captive bred Betta Fish are the result of decades of line breeding and will fight long past the point of exhaustion, sometimes for hours.

Today, Betta Fish are known for their vibrant colors, intolerant tempers, and ease of care. They are kept in bowls and vases worldwide as showpiece specimens.

There are several species of Betta in the region. All are territorial to varying degrees but few are as aggressive as captive bred Betta splendens.

Why Do Betta Fish Fight?

Whether wild or captive bred, the males of all Betta species are territorial to a degree.

While they live in small bodies of water they will defend patches of floating weeds and still water from competitors for females and real estate.

Like many Gourami relatives, Bettas build bubble nests out of mucus and air bubbles. Finding the ideal spot is not easy.

These bubble nests are stationary and the males have to defend the spot lest other males crowd the area and prevent him from mating with ready females.

How Does Betta Fighting Unfold?

Once they see each other Male Bettas start a sparring match by deepening their colors, and flaring out their fins as well as their operculum (gill cover).

A gauzy flare of folded skin also unfurls around the chin, making the Betta appear much larger when viewed from the front. Many territorial fish have these, including Cichlids.

The challenger will most likely answer with a similar display of his own. From there, they lash at each other with rigid tail slaps and even head butts.

Assuming neither Betta Fish backs down they quickly escalate into violence. Tail slaps and bites are the weapons of choice and the males spin around each other dramatically until one backs down.

During the display they also gulp additional air as fighting is exhausting for them.

As long as one male can escape the fight and exit line of sight of the winner these matches are rarely fatal. However, despite their small mouths and usually short bouts, Betta fights aren’t harmless.

Fins get ripped, which are open wounds that can get infected, and while scales usually remain intact an unlucky bite can puncture an eye.

The stress and exhaustion brought on by a match can also lead to problems.

For starters, because Betta Fish are bred for aggression, even a male that loses will let himself be drawn into a new fight with ease, no matter how exhausted he is. And as partial air breathers, a defeated Betta will be provoking the winner every time he returns to the surface for a gasp of air.

Eventually, one or both fish die of exhaustion in a small tank.

Betta Fish fighting behavior can be easily provoked by their reflection or even a fingertip, which provides a similar profile to another male Betta staring down an enemy.

The Betta will flare its gills and go into full fight mode even though the mirror or fingertip never tires. Some pet stores sell “exercise mirrors” for Betta Fish that cause them to lash out at the supposed intruder.

What Does This Mean for Aquarists?

Now that we know how and why betta fish fight, let’s look at what this means for the average aquarist.

Betta Tank Mates

Tank mates will generally be spared the attentions of a male Betta Fish. Similar looking fish may provoke a response, however.

Male Fancy Guppies, with their long flowing fins, are a prime target for aggressive males.

Usually, the main issue with Bettas in community tanks is choosing fish that won’t nip at their long flowing fins. Betta Fish will occasionally give short chase to tank mates but overall are great community residents!

Multiple Male Betta Fish?

Believe it or not, you can keep more than one male Betta Fish together (under certain circumstances).

Multiple male setups have to be approached like keeping Rift Lake Cichlid displays. You just have to recognize that there will be fighting going on and plan accordingly.

Large aquariums (40+ gallons) with plenty of decorations and heavy plant growth are necessary to break up line of sight and allow males to create distinct territories, as they would in nature.

You’re also better off keeping 4 or more males rather than only two, to spread the aggression around. The Betta Fish will display and occasionally spar but with the amount of room provided nothing serious will break out.

Death matches usually occur in smaller tanks. Adding one female per male also helps take their attention away from fights.

Breeding Bettas

Male Betta Fish will nip and attack females that aren’t ready to breed.

If you keep a female Betta with a male, you should have a fairly spacious, planted tank of 20+ gallons to ensure the female can escape his constant attention. The male will eventually create a bubble nest near the surface and carve out his territory there.

However, he will give chase to the female whenever she surfaces for air and can worry her to death in a smaller tank.

Many Betta breeders keep the female in a separate hanging cage or a divided aquarium until she begins developing eggs in order to protect her.


Betta Fish fights are something you can work around with a bit of planning. The majority of aquarists simply keep a single male as they can live solo or in a community tank with few issues. Adding social outlets makes them even more interesting and well worth experimenting with, however!

Jason Roberts
About Jason Roberts
Jason is an aquarium fanatic that has been a fish hobbyist for almost three decades.

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