Why Do Betta Fish Fight? 10 Reasons For Their Aggression

    why do betta fish fight

    Bettas are one of the most interesting fishes to keep in the hobby, but one of the most-asked questions that a beginner would have is “Why do Betta fish fight?”

    As an aquarist, we need to know about the behaviors of the fishes we are keeping so that we can give them a fulfilling and interesting life. That said, you need to understand that Betta fishes fight both because they are aggressive by nature and there are external factors that aggravate them.

    In this article, let’s talk discuss everything about this interesting Betta fish behavior and what good aquarists should do about it.

    Why Do Betta Fish Fight? 10 Main Reasons

    betta fish fight to death

    Betta fishes fight because they are inherently an aggressive species, so they naturally have a very short fuse. Plus, there are a lot of external factors that a Betta fish might have to deal with in an aquarium.

    In this list, we’ll go over the top reasons why your Betta fish are always aggressive and fighting other fishes.

    1. Predatory Instincts

    Betta fishes are near the top of the food chain in their natural habitat. Due to this, they are not used to showing submission and are instead more likely to be aggressive to other animals who seem to challenge their role.

    Bettas have instincts telling them to fight and hunt as they please because, under natural circumstances, few can challenge them.

    Wild Bettas are known to be highly aggressive, especially to other Bettas.

    Of course, this isn’t the case in an aquarium. Your aquarium is not your Betta’s natural habitat, but they don’t know that, so their instincts are still all fired up even when there’s little cause to do so. This is the core reason why most Bettas get into fights.

    2. Territorialism

    When an animal is territorial, it means they’re not used to sharing their space with other animals.

    This is also an instinctual thing, relating to the first item. In the wild, Bettas typically have wide bodies of water to establish territories in. This means that they can safely defend a territory, and they do. This species is known to fight to the death to defend its home. That said, it’s relatively rare for them to encounter challenges.

    But an aquarium is much, much smaller. Bettas perceive other fishes as a threat to its territory and thus get into fights with them, especially if they’re similar-looking.

    3. Pent-up Energy

    Just like people, animals get restless too. Bettas are especially prone to these tendencies.

    If you’ve owned a Betta before, or currently do, you’ll notice that they’re very active swimmers. Despite their long, elegant fins, they actively explore their tank and interact with the objects. They spend their day using up their energy.

    Bettas that haven’t been active are more likely to be aggressive because the pent-up energy needs some form of release.

    Just like humans when they’ve been cooped up for too long, your Betta might just need a little bit of exercise and stimulation to keep them more active and less aggressive.

    4. Overcrowding

    Bettas could also be aggressive because of an overcrowded environment.

    We’ve already established that these animals are naturally aggressive and incredibly territorial. Well, those two core tendencies are put to the test when they’re put in an overcrowded tank. Betta fishes need their space, and they need to be the top dog.

    If they’re in an overcrowded tank, they will always feel threatened and feel the need to establish hierarchy and territory by attacking other fish.

    5. Small Swimming Space

    In the wild, Bettas live in slow streams and shallow bodies of water. Although they don’t like deep waters, they’re used to a wide swimming area to explore and work their energy.

    An aquarium is much smaller compared to a Betta’s natural habitat, and this problem is compounded if you intentionally put Bettas in places smaller than the minimum recommended volume of 5 gallons.

    Their nature for exploring their surroundings is likely to make them restless if they don’t have enough space to explore. This stress often translates into aggression that they then release to other fishes or animals around them.

    Betta fish need to swim to stay healthy. If they are not given enough space to swim, they may become frustrated and aggressive. In the wild, Bettas will often swim long distances in search of food or mates.

    6. Illness or Injury

    Bettas are also more likely to fight other fishes when they are experiencing stress through sickness or injury.

    When in pain and feeling vulnerable, predatory animals like Bettas tend to compensate by being more aggressive so as not to appear weak.

    In the wild, this makes it so that Bettas aren’t attacked by other fishes, even when they’re sick. In your aquarium, however, this just serves to antagonize other fishes. Be sure to know what kind of illness your Betta has to provide the right medicine, like API White Spot Treatment for Ich or API Fin & Body Cure for general illnesses.

    7. Protecting Their Eggs

    Bettas make bubble nests to lay their eggs on until it’s time for them to hatch. But for many fishes, Betta eggs are a delicious treat, so the Bettas have to protect their nests. In the wild, it’s not uncommon for male Bettas to fight to the death to keep their eggs from being eaten.

    8. Intentional Breeding

    Some Bettas are more aggressive than others, and yet some are bred exactly for their aggressiveness. Some parts of the world breed and train Betta fish for fighting events, creating extra aggressive species that will fight other fishes at the drop of the hat.

    9. Stress

    Just like all other types of animals, stress does things to a Betta fish. When humans become stressed, they can be easily irritated and prone to anger and other quick emotions. When Betta fishes are stressed, they tend to express that stress through fighting tendencies.

    Many different factors can cause stress to your fish. Overcrowding, bad water quality, sudden loud noises in their tank room, etc., can stress them out and make them more aggressive.

    10. Hunger

    Hunger is kind of a double-whammy for Bettas. On one hand, hunger is another source of stress that can make them aggressive. On the other, as predatory fishes, Bettas tend to hunt when hungry.

    Remember that in the wild, Bettas are top predators, so when they get hungry, their predatory tendencies are triggered, and they tend to hunt more actively, fighting other fishes for food. Be sure to give them nutrient-rich foods like Tetra Betta Small Pellets and Fluval Bug Bites.

    What Happens When Betta Fish Fight?

    Seeing your Betta fight with another can be pretty terrifying.

    If you want to know what happens when Betta fish fight, we can take a look at a traditional “Betta fish fight.” This kind of activity is illegal in the US, but it used to happen in other parts of the world where Bettas live.

    Most Betta fish fights are fights to the death. The matched Bettas are placed in one tank, and the fish square off, lunge, and tear each other’s fins and scales apart with their powerful mouths. Some fights last mere minutes, while others can continue for more than three hours.

    Fighting ends when one fish disengages and furls its fins or dies. It’s a terrible practice that deserves no place in the modern world – which is also why you should make sure that your pet Bettas won’t have to go through the same ordeal.

    How Do You Know If Your Betta Is Aggressive

    are betta fish aggressive towards humans

    In some fish species, there are no outward signs of their aggressiveness. This is not true for the Betta splendens, who will proudly create a display to indicate that they’re ready to fight. If you’re worried that your Betta may be an aggressive one, watch out for these signs.

    Flaring Fins And Gills

    This is the famous “display” that Betta fishes are very well-known for. When feeling aggressive, Betta fishes extend their gills and all the fins in their body to appear more threatening.

    We can see many animals do the same type of display when threatened. Housecats, for example, make the fur on their back and tail stand, extend their claws, and flex their bodies to appear bigger than they are.

    It’s a natural response by animals to threaten their opponent in the hopes of being left alone without any fighting.

    Betta fishes are much the same. Their long, flowing fins and vivid colors all serve some warning purpose in the wild, but their characteristics have been selectively bred to create a more visual display.


    After flaring their fins, the Betta fish will square off with their opponent in kind of an old-fashioned “stare-off.” Regardless of whether they stay still or rotate around their opponent slowly, they will keep their eyes on their opponents and wait for an opening to attack.

    Most displays end here if the fish is intimidating or asserting dominance. When it proceeds to the next stage, however, you know that you’ve got a fight on your hands.


    This is usually the point when you can determine if your Betta is “being serious” or not. When Betta fish lunge for the other fish, they are either threatening them to stay away or trying to get a chance to bite their opponent.

    Nevertheless, when a Betta fish starts to lunge for another fish or another Betta, you’ll want to put them in different tanks, as it will most likely escalate.


    Betta fishes will then start to bite other fishes’ fins. Whether they’re fighting another Betta or a different kind of fish, their quick strikes will usually allow them to bite and tear at their opponent’s fins.

    Injuries in fish can very easily lead to stress and infection.

    In most cases, the health of a fish will decline if they get a severe injury. If you don’t want this to happen, it’s best to separate the Betta fish into another tank.


    Being aggressive predators, Betta fish usually fight to death. Thus, they won’t back down just because the other fish turned tail and ran away. The Betta fish will take care of the job by chasing the other fish wherever they go in the tank.

    Nipping Fins

    When a Betta fish doesn’t actively bite and tear off its tank mate’s fins, it will most likely harass the other fish in the form of nipping.

    Nipping is similar to biting in fishes, although it’s not as intense. Nipping means that the aggressor is harassing the other fish with several small bites out of their opponent’s fins whenever they get the opportunity.

    Do Male and Female Betta Fish Fight?

    Male Betta fish are extremely territorial and will fight whatever enters their territory without reserve – even other Betta fish, male or female.

    However, female Betta fish don’t stimulate the same kind of aggression as males do in other males. Plus, several factors could minimize or remove this aggression entirely. These Betta fish aggression factors are listed below:

    • When two Bettas are put in a small tank, they will fight, regardless of sex. However, when given enough space, the male can establish its territory while still giving the female plenty of swimming space, minimizing aggression.
    • Male Betta fish are more likely to be aggressive when they see the other fish. An abundance of cover to break up the line of sight can hide the female, and in a big enough tank, they can both live peaceful lives without seeing each other often.
    • Breeding season will change the male’s tendencies towards females. Aggression will be replaced by the desire to mate. This will start to happen when the males begin to create bubble nests.

    How Do Betta Fish Fight? Signs Of Fighting

    Betta fishes display the same aggressive tendencies when they fight another Betta fish, especially when two males square off. These signs are the following:

    • Bettas extend their fins and gills when they are assertive. This always happens when faced with another male Betta.
    • If left alone, two male Bettas will square off with each other in an attempt to intimidate.
    • After squaring off, the Bettas will then lunge at each other to further scare the other Betta away. Lunges can either be scaring tactics by themselves or done to gain the upper hand in biting.
    • Bettas will bite and tear at each other’s fins until one gives up.
    • When one of the Betta fish turns tail and runs away, the winning Betta will chase the losing one to initiate more fighting. This can also result in death.
    • Bettas will also harass and nip at the other Betta’s fish while swimming. This is when a Betta will take small bites out of the other’s fins.

    How To Stop Betta Fish From Fighting

    how do i stop my betta fish from fighting

    As responsible hobbyists, we all love our Betta fishes, and we don’t want them to get hurt.

    Thus, there are times when it becomes necessary to know how to stop a Betta fish from fighting – whether to save another fish species, another male Betta, or a female Betta. Here are some tips.

    • Separating the Bettas. This is the simplest and most effective way of stopping a fight. All Bettas will stop being aggressive once they see that their enemy isn’t in the same tank anymore.
    • Using a divider. If you can’t put individual Bettas in separate tanks, you can also opt to put a divider to separate the two Bettas at opposite ends of the tank. This will achieve the same effects as quarantining the Bettas, although the space will be smaller. Even a transparent divider will do; they will still flare when they see each other but can do little else.
    • Training Betta fishes not to fight is vastly more time and resource-intensive, but it’s possible to do by rewarding peaceful behaviors and discouraging fights through punishment.
    • Removing stressors. Dirty water, hunger, overcrowding, disruptions in the water – all of these and more can lead to stress and aggression in Bettas. Minimizing stressors and making sure your fish is living a healthy, fulfilling life will minimize fighting.
    • The only way to stop your fishes from fighting is to see it firsthand. Keep a close eye on your fish and be ready to intervene if something is indeed happening.

    Do Bettas Fight Other Fish Species?

    Bettas are naturally highly aggressive and territorial, so it might not surprise you that they indeed will fight other fish species.

    That said, there are some types that Bettas like to fight more, while there are also some that they don’t – and can’t – touch.

    Here are the species that Betta fishes often fight the most.

    • Fishes with long flowing fins. Guppies, angel fishes, long-finned platys, etc., will likely be seen as a threat because they resemble Betta’s flowing fins.
    • Slow-moving fishes. Species that can’t get away fast enough from a Betta’s attack are highly vulnerable to this aggressive fish.
    • Small species and fries. Bettas eat other fishes, especially those that they can fit into their mouths. Thus, fries are not safe from their attacks.


    Betta fishes are great fun to keep and raise, but their aggression is a pretty significant part of keeping them.

    Responsible owners need to know why and how they become aggressive to prevent it from happening and ensure that their Bettas – and any other fishes that might be housed with them – can live a long and fruitful life.

    Recommended Reading:


    Don’t miss out on valuable tips! Subscribe below for our newsletter and get weekly updates on newly published posts.

      We respect your privacy. Unsubscribe at any time.