Why Do Betta Fish Expand Their Gills? (All You Need To Know)

When you watch your betta fish for some time, you will notice them expanding their gills and fins towards you and other fishes. Have you wondered why? There are many reasons for betta fish flaring its gills and fins. So, why do betta fish expand their gills? Let us find out.

Betta fish are very aggressive and territorial and expand their gills to show aggression or dominance when they see other fish or any potential threat. Expanding gills and fins make them look bigger and more intimidating, which helps them to scare off predators and intruders.

This article will also discuss how to stop our betta fish from flaring. So, let us get into it.

Why do betta fish flare their gills?

Betta fish flare their gills to look bigger and more intimidating so that they can assert dominance and scare off any potential threat.

It is their natural behaviour, and there is nothing to worry about. 

Bettas are known to be aggressive and territorial fish. 

They will flare to protect their territory and scare off their potential threat.

Gills are present right behind the head of your betta fish and are clearly visible when they flare and expand, which makes them look bigger.

Let us discuss all the reasons behind your betta fish expanding its gills:

  1. Betta fish expands its gills and fins to intimidate potential threats.
  2. They do this to assert dominance.
  3. Betta fish flare to protect their nest
  4. Betta fish will flare to show aggression.

Intimidating potential threat

Bettas make a bubble nest using saliva and air when ready to spawn.

Betta will try to keep any other fish and potential threats far away from the nest.

For this, they will intimidate the potential threat by expanding their gills.

Assert Dominance

Betta fish are aggressive and territorial fish and doesn’t like any other fish to enter their territory.

Betta will flare their gills and fins to scare off and warn of any potential threat entering their territory or threatening betta.

Even a betta will not like another betta to enter its territory and will fight until one dies.

This is why keeping two male bettas together is not advisable.

Protect their nest

Betta fish make a bubble nest to keep their eggs in the nest and protect it from predators.

Protecting eggs and fry until they can swim independently is a responsibility of a male betta. 

So, to protect it, betta will scare off other fish or any threat by flaring its gills and fins.

Show aggression

As we know, bettas are very aggressive creatures and will show aggression when feeling threatened or trying to assert dominance.

They can show aggression in all these situations:

  1. When there is competition for food.
  2. When there is a presence of incompatible mate present in your betta tank
  3. When some other fish is trying to enter your betta territory
  4. When your betta is feeling threatened or weak

Your betta fish will try to look bigger, and for that, they will expand their gills and fins to show aggression. 

Is it normal for a betta fish to flare their gills?

It is normal for a betta fish to flare its gills.

Even it is a sign that your betta fish is healthy.

However, betta fish flaring its gills most of the time indicates something wrong.

Also, too much flaring will stress out your betta fish.

So, if your betta fish is flaring its fins most of the time, you should get concerned and try to find the reasons for such.

Flaring gills is a natural behaviour of a betta fish to assert dominance, threaten other fish, and protect itself and its bubble nest from other fish.

But flaring too much or unnecessarily is a sign of something wrong.

Let us discuss all the reasons why betta fish expands their gills.

How to stop my betta fish from flaring?

Ensure all these things to stop your betta fish from flaring:

  1. Avoid adding incompatible tankmates to your betta tank.
  2. Create plenty of hiding spots for your betta fish.
  3. Ensure your betta fish is living in a large enough tank.
  4. Ensure adequate water parameters.
  5. Try not to be around the tank every time.
  6. Place your betta tank where there is no noise or other disturbance.

Avoid adding incompatible tank mates.

Bettas are aggressive and territorial and will not like every fish to live in their tank.

Fishes bigger and more colourful than your betta fish should not live with your bettas.

Even two male bettas cannot live together, as they will fight each other until one of them dies.

These are some of the fish you should avoid keeping with your bettas:

  1. Other bettas
  2. Goldfish
  3. Angelfish
  4. Cichlid
  5. Ghost shrimp
  6. African frog

Also, if your bettas are uncomfortable living with their compatible mates, you should remove the fish and let your betta fish live alone.

You can detect if betta fish is okay or not living with its mates by noticing all these behaviours:

  1. Betta fish flare gills towards the mate most of the time.
  2. Betta mates are trying to nip or chase your betta fish.
  3. Your betta fish is hiding most of the time and also started avoiding eating.

Create plenty of hiding spots.

Betta fish require hiding spots to hide whenever they feel weak or vulnerable. 

Also, betta fish need a hiding spot to rest whenever they want to.

Creating plenty of hiding spots for your betta fish will help prevent stress and aggression from your bettas.

Creating hiding spots will prevent stress, which will reduce the number of flaring. 

Now, there are various options when it comes to creating a hiding spot for your betta fish. You can go by adding terra cotta pots, caves, sunken ships, rocks, and plants.

Adding caves and live aquatic plants will make a good hiding spot for your betta fish.

Ensure a large enough tank for your betta fish.

Betta fish live in shallow places like rice paddies, marshes, stagnant ponds, and slow-moving streams in the wild. 

Places where betta fish live in the wild make us think bettas can thrive in a small bowl or tank. 

However, this is not true; betta fish require large enough space to live and swim comfortably.

Bettas require large enough space to swim around and explore. Small tanks will cause stress to them, resulting in more flaring.

Consider providing your betta fish with at least a 5-gallon tank. A 10-gallon or bigger tank will be an excellent option.

Ensure adequate water parameters.

Bettas can easily get into stress when living in a tank with inadequate water parameters.

Due to stress, betta will flare its gills to expel some tension. 

So, it is necessary to ensure adequate water parameters and ideal living conditions for betta fish to stop them from flaring.

To ensure adequate water parameters and ideal living conditions, make sure of all these things:

  1. Water temperature should be between 78-82 °F.
  2. Add a heater to keep the water temperature stable, as the unstable water temperature will cause stress to your betta.
  3. Maintain the water pH level between 6.5 and 8.
  4. Keep a regular check on ammonia, nitrite, and nitrate levels.
  5. Maintain ammonia and nitrite at 0 ppm, whereas nitrate should be below 20 ppm.
  6. Perform a 30-35% weekly water change to ensure clean water conditions. 
  7. Add a filter to your betta tank to ensure clean water conditions and protect the water from harmful toxins like ammonia and nitrite.
  8.  Make sure to provide your betta fish with gentle water flow.

Also read: Best Water For Betta Fish?

Try not to be around your betta tank every time.

Bettas tend to flare at their owners because they are happy to see them.

There is nothing to worry about as it is their natural behaviour, and they are simply saying “Hello” to the owner.

However, the other reason can be that they see you as a threat and flare at you.

Now, if you do a quick movement and suddenly step towards their tank, they will see you as a threat and flare at you.

Also, you must know that bettas are sensitive to noise and movement. So, if you create noise or move around your betta tank more often, they will flare as a response.

So, try to be less around your betta tank or have a slow movement near their tank.

Place your betta tank in a quiet place.

As discussed above, bettas are sensitive to noise and movement and will respond by flaring.

So, you should consider keeping your betta tank in a room where nobody comes, and there is not much noise around.

Do female betta fish also flare?

Female betta fish do flare their gills and fins.

Yes, they will not flare more often like male betta fish, and there is a reason for that.

A female betta fish is less aggressive and territorial than a male betta.

Female betta will flare its gills whenever it feels threatened and vulnerable.

If you have incompatible tankmates in your female betta tank, you will see your female betta flaring gills as a sign of aggression.

Also, if you have a male and female betta in the same tank, you will see female betta flaring gills and tails.

This is because the female betta will feel threatened by the male betta, and flaring its gills and fins will help her assert herself and keep the male betta away from her.

Mostly all betta fish flares their gills as it is their natural behaviour. However, you may find some betta fish who rarely flare their gills.

Also, some bettas don’t have the instinct to flare. It is due to genetics, and we cannot do anything about it.

Are there any benefits of flaring in betta fish?

All these are the benefits of flaring in betta fish:

  1. Flaring helps betta fish to release excess stress.
  2. Betta fish release extra energy by flaring.
  3. Flaring helps betta fish do exercise by stretching their muscles and fins.
  4. Betta fish look intimidating when they flare their gills and fins.
  5. Flaring helps betta fish attract their mates.
  6. Flaring also helps them calm down.

Release excess stress

Betta fish can come under stress because of various reasons like inadequate water parameters or incompatible and nippy tankmates. 

In such a case, betta will flare its gills to release tension.

Release extra energy

Bettas are active swimmers and like to swim from one corner to another. 

They have so much energy that they flare their gills and fins to release some. 

You will notice your betta fish swimming crazy after flaring sometimes. 

Don’t worry; it is a good sign and indicates that your betta is healthy and full of energy.

A good exercise of muscles and fins

Flaring is also a good way to exercise muscles and fins for your betta fish.

When betta fish flare their gills and fins, it stretches their muscles and fins, which helps keep the muscles and fins healthy.

Many betta keepers encourage their betta to flare their fins and gills by adding a mirror in their tank.

Adding a mirror in their tank will help your betta see its own reflection, and your betta will try to fight and assert dominance, thinking of that as another betta fish. 

In this process, your betta will flare its gills and fins. 

So this way, you can encourage your betta fish to expand its gills and fins if your betta fish don’t flare much.

However, we don’t recommend showing a mirror to your betta fish if doing such a thing causes too much stress to them.

Also, you should only show the mirror to your betta fish for some minutes.

Look intimidating

Betta fish expand their gills and fins to scare off predators, other bettas, and any potential threat.

They also do that to assert their dominance. I had dwarf gourami, betta, and neon tetras in a tank. My betta fish made a bubble nest in the left corner of the tank, and whenever gourami reached that section, it flared its gills towards him. 

So, betta fish also do this to protect their bubble nest and eggs from other fish or any potential threats.

Attract mates

Betta also flared its gills and fins to attract mates in the wild. 

In captivity, they will do the same and expand their gills to look bigger to attract their mates.

This is mainly done by the male betta fish as female betta fish are not interested in attracting males, and males always have to approach the female betta.

A betta will attract a potential mate by flaring its gills and fins whenever it wants to breed.

Clam down

Betta fish also expand their gills and fins to calm themselves down.

Flaring gills and fins help betta fish release the stress hormone named Cortisol.

When betta fish are too excited, they release Cortisol hormone into their body, and you must know that too much Cortisol in your betta fish can harm them.

So, betta fish flare their gills and fins to release the hormone and calm themselves.


Betta fish expands its gills to look bigger, which helps assert dominance and scares off predators and other potential threats.

Bettas are aggressive and territorial creatures and don’t like other betta and any other fish to enter their territory. And to assert dominance and proof that he is the boss here, he flares and shows aggression to other betta and fish.

Flaring gills and fins are not harmful to bettas until they do this regularly.

Bett flaring its fins and gills most of the time is a sign of something wrong.

Sometimes betta fish also flare to release stress, to be calm, and to release build-up energy.

Reference: ResearchGate, NCBI

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