Why Is My Betta Fish Flaring Its Gills

Male Beta

Fish are a lot like people. There are quirks of body language that you might not always understand right away. Some things are hard to decode if you don’t know the reason behind it. For example, betta fish and their flaring gills.

You might notice that your betta will puff out their gills and fins at different times and wonder, “Why is my betta fish flaring its gills at me? Does it hate me?”

Most likely, they don’t hate you. In fact, there are several reasons why your betta fish is flaring. Today, we are going to explain the reasons and give you some valuable insight. That way, you can decode the reason and make adjustments to keep you betta happy and healthy.

Let’s get started.

Reasons Why Betta Fish Flare Gills

There are plenty of reasons why your betta fish is flaring its gills. Most of it is an instinctive reaction, but noticing when your betta flares its gills can give you a lot of insight into how your fish is doing.

Let’s have a look at some of the common reasons why a betta fish will flare its gills:


In the wild, whenever a fish enters a betta fish’s territory, the first reaction of the betta is to puff up by flaring their gills and fins. Think of it like a dog or cat that bristles their fur whenever they are trying to look bigger than what they really are. This is meant to do two things: essay that the other fish is unwelcome and that they are against something far stronger or bigger.

Obviously, this puffed up display will not work on bigger fish in the wild or aquarium, but it does the trick for smaller fish or ones about the same size as your betta. In fact, flaring is most effective on other betta fish. More passive species may be too oblivious to understand.

However, while you might think this flaring happens all the time, it is less common in the wild. Feral betta fish have shorter fins and are less aggressive than their domesticated counterparts.

They may even hide when encountering other fish that are of another species. On the other hand, in captivity, betta have no choice but to intimidate those who come into their territory.

Betta Fish flaring grills


But what if your betta fish isn’t flaring at others for intimidation? What if its flaring its gills at something else—like itself? Keep in mind that many animals, betta include, fail the self-recognition test. They will not recognize that images seen on the surface of objects is their reflection. Because of this, a betta will often attack its own reflection.

Since this can lead to injuries, you should try to get rid of any reflective surface or glaring that will cause a reflection.

Change the position of the lights near the aquarium. If you can’t stop the reflection, you might want to put up some kind of cover, like a curtain. You can even paint the sides of the tank to prevent too much reflection.


As you can imagine, the main reason a betta flares its gills is due to a stressful situation. Something is deemed a threat, and the betta reacts by trying to defend itself or attack.

Because your betta cannot do much aside from flaring, it will become extremely stressed. Sometimes stress alone is enough to make them flare out. Think of it as a sign of frustration.

Some betta fish will stop eating and won’t sleep. The stress will start to tax their immune system, and that can lead to issues with bacteria and fungus.

Try to keep your betta from flaring too often. Eliminate mirrors and other things that could potentially make it feel too stressed out.

Another reason your betta might be displaying signs of stress is due to an overcrowded tank or their tank mates (which we discuss below). They might be getting agitated because they do not have enough room to swim.

Mating Display

Now, while some situations are considered stressful, there is one time when a betta will flare its gills that isn’t bad. Breeding is that time.

Males will usually flare at females as a way to introduce himself; if the female accepts, she will become submissive. Once the male establishes dominance, the flaring will stop. However, if flaring continues, separate the male and female.


Another thing to consider is excitement. You will notice that betta fish are all unique. Sometimes, they flare when they are angry.

Other fish will flare when they are happy. Flaring can happen without aggressive body language. For example, when you feed your fish, they might flare at their food out of happiness.

If your betta isn’t extending their fins but flaring their fins, they might be playing a game with you or displaying a quirk of their behavior. In this case, it is perfectly fine to let them have their fun.

Tank Mates

The aggressive nature we described early translates over to how a betta fish will interact with tank mates as well.

Even if you have a more docile betta that doesn’t mind sharing waters with tetras or whatnot, it may still decide to flare its gills once in a while. Sometimes, more aggressive betta will even attack their tank mates if they get too close.

The problem with a betta flaring its gills at tanks is that most schooling fish won’t understand the meaning. Most fish aren’t known for flaring their gills, so other fish don’t take heed.

This often leads to the betta going on the offensive and attacking them. This includes shrimp and snails, which often become targets of aggressive betta.

Be sure to research the best tank mates for betta fish before filling up your tank!

Is Gill Flaring Bad For Betta Fish?

So, as we mentioned before, flaring can be stressful. It can be very detrimental when done in excess. Some people will purchase mirror toys of their bettas, which are meant to trick the fish into thinking that there is an enemy betta nearby.

The flaring will let the fish stretch and tone their muscles and keep them on their toes, so to speak.

However, if this happens too often, it will lead to overexertion. Imagine it like running for several hours every single day without rest. You’ll get burned out, right? It’s the same for your fish.

If you decide to buy one of those toys for your betta, limit use to around 20 minutes a week. This will stop your fish from getting too stressed.

Why Is My Betta Flaring At Me?

This might be shocking, especially if you are giving your betta fish a lot of tender love and care. You might be inclined to think that your fish hates you. This likely isn’t the case.

Rather, your fish might simply be telling you to back off after a stressful moment, such as returning to its tank after a cleaning or being woken up. Sometimes, it could just be that your betta fish is a character.

However, one reason that often goes overlooked is that you just got this betta. In that event, it is not used to you and your meddling yet. The fish might be afraid. Don’t worry, though. Your fish will eventually bond with you, but until then, be patient and don’t do anything to induce too much stress.

Is There a Way To Stop a Betta From Flaring Its Gills Too Much?

Yes, there are ways to stop a betta from flaring. Some of those ways we have already touched on, such as limiting exposure to mirror toys, finding more passive tank mates, and also reducing glare on the walls of the aquarium.

If that doesn’t work, you might want to try changing things within the tank itself. Test the water to make sure that it isn’t full of ammonia, nitrites, and nitrates.

Look to see if your fish is intimidated by you or if it’s flaring at its food or other things. You might have to change the food or swap around the decorations.

Eventually, you will figure out what is causing your betta to flare.

Yellow Betta

Do Female Betta Fish Flare Their Gills?

You might be wondering if fin and gill flaring is a solely male reaction to intimidation, stress, and breeding. Surprisingly, female betta fish will also react to certain stimuli by flaring their gills.

Being that they are less aggressive than males, females will not always flare at tank mates or their reflection—but sometimes they will.

When females flare, it often has less of a defensive purpose. That is why, if you give a female betta fish a mirror toy, she might not react to it.

That is why you can sometimes keep female betta fish in the same tank but can never mix males.

Still, just because you do not see your female betta flaring her gills, it doesn’t mean you can be less lax with tank set up. Always make sure you are making a tank with plenty of hiding spaces and friendly tank mates. That way, you don’t induce too much stress.

Recap: So, Why is My Betta Fish Flaring Its Gills?

So, let’s recap. “Why is my betta fish flaring its gills” is a common question among betta fish owners. Hopefully, you now understand that flaring is a kind of act, a message sent from the betta fish that is meant to be intimidating. Your fish wants to be bigger than its opponent. However, it could also mean you have a stressed out betta.

Assess the situation. Watch your fish to see what is happening. If your betta is flaring too much, you are going to want to somehow stop the behavior, because it can be harmful in the long run.

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