Why Do Betta Fish Fight? Signs of Aggression and How to Stop It

Betta fish fight or show signs of aggression for a variety of reasons.

The most common reason for betta fish fighting is to establish dominance over their territory. They may also fight when they’re feeling stressed, protecting their eggs, intimidating other tank mates, or living in overcrowded tanks.

It’s common for betta owners to ask “why do betta fish fight?” So, If you want to learn more in-depth about the reasons why betta fish fight and what you can do to stop it, then this article is for you!

Why Do Betta Fish Fight: Are They Naturally Aggressive?

If you’re wondering what could possibly make these small peaceful-looking creatures fight in the first place, let us tell you that it’s not just bettas that fight.

Many fish breeds can show aggressive behaviors such as fighting or nipping on each other’s fins, but bettas can take it up a notch!

Here are some facts many don’t know about bettas:

Betta fish are a very territorial fish breed, and that’s why they’re considered naturally aggressive. It’s because of that behavior that they’re also known as “siamese fighting fish”.

However, we don’t know exactly whether this aggression is innate or if it’s just a result of how they’re being reared.

This territorial behavior may have developed as a result of the limited food resources available to bettas in their natural habitat.

When there isn’t as much food available, bettas can start to fight over it and become territorial to guard their food supply against other fish.

Betta fish, Siamese fighting fish with green plants and blue background

Common Causes for Betta Fights

You may be thinking now: if bettas fight over limited food supply in their natural habitat, what makes them fight in an aquarium where they have constant food supply?

Well, the answer is: Not just one, but a handful of reasons.

Other factors contribute to betta fish fighting, and the following are the most common:

Stressful Conditions

Some living conditions can cause betta fish to become stressed and, as a result, more violent. These conditions include:

  • Male bettas chasing around females for mating. This happens more often when there are multiple males in one tank or when females are outnumbered by male bettas
  • In some cases, female bettas will start fights when they’re stressed by males as well
  • Poor or changing water conditions
  • Poor nutrition
  • Keeping betta fish with other aggressive breeds in the same tankProtecting Their Egg Nests

When male bettas want to mate, they build egg nests to attract females.

If other males enter the territory where the male bettas have built their egg nests, they’ll start fighting the intruders to keep them out and protect their mating chances.

What’s more, after mating, male bettas are responsible for protecting the offspring in the egg nests until the babies grow enough.

Overcrowded Tanks

It’s common for betta fish to start fighting when they’re in an overpopulated tank since crowded aquariums tend to make them stressed.

Other Stimulants

Bettas aren’t only stimulated by other fish attacks. Rather, they often feel intimidated by inadvertent actions such as:

  • Sudden movements around them, especially from fish with large gills or fins
  • Other tank mates that have bright colors

Are Female Bettas Also Aggressive?

Female betta fish are generally less aggressive than males. However, in certain situations, female bettas can also show aggression to other females or even male bettas.

When female bettas are kept in groups, they form what’s known as a sorority or a harem with an established social hierarchy.

After that, when another female betta is added to the same group tank, they might be aggressive towards her for a while until that hierarchy is re-established once more.

Signs of Fighting and Aggression in Betta Fish

Bettas don’t start physically attacking other tank mates right away. If you take a close look at the right time, you’ll be able to easily spot these fights a while before they happen.

This is what a betta fight looks like:

  • A betta fish fight usually begins with a betta fish that feels intimidated, so it starts giving gill or fin flares, which are warning signs to the other fish.
  • If the other fish doesn’t leave after these warnings, the fight might escalate to other forms of physical violence such as fin and tail nipping or ramming.

Note that: If you notice that one or more of your fish are injured, not eating properly, or showing changes in their behavior, this probably is an indication that other tank mates are harassing or attacking them.

For tanks where aggressive fish breeds are kept, it’s best to add plenty of live plants and decorations to the tank. This provides a safe shelter for the fish that are being harassed, especially the ones smaller in size.

These hiding spots are also perfect for fish to lay their offspring and keep them protected against any attacks.

White Blue Purple and Pink Betta

Can Betta Fish Kill Each Other?

If bettas are kept in proper tank conditions with enough decorations, it’s unlikely that they’ll attempt to kill each other.

However, it’s possible that two male bettas will fight each other to the death if the fight isn’t broken off soon enough.

How to Stop Betta Fish From Fighting?

You don’t have to deal with constant betta fights with each other or other tank mates! These are some of the precautions you can take to prevent frequent fighting in the aquarium:

  1. Limit the number of male bettas to one male per tank to avoid territorial behaviors
  2. Males separated in different tanks should also have visual barriers so they won’t see each other often
  3. Remove mirrors as well since bettas can react to their own reflections
  4. Avoid keeping tank mates with large fins and bright colors in the same tank with your bettas since they can startle your bettas
  5. Provide the tank with enough live plants and decorations that act as hiding spots, but make sure the decorations won’t pull on the bettas’ large flowing fins


Betta fish are beautiful and one of the popular choices for small house aquariums, but they sure come with a side of personality and temper!

After we’ve answered your question “why do betta fish fight?” and discussed how to limit their fights, you now know how to keep your betta friends in peaceful and safe conditions.