Betta Fish Tumors: Why They Happen & What To Do

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Last Updated on 2023-08-26

If you notice your betta fish has a tumor you may begin to panic. After all, you’ve cared for them for so long. However, while tumors often signify the end of your betta’s life, you may not need to worry just yet.

Keep reading to find out what to do if you notice your betta fish has a tumor, as well as what they look like, how to prevent them, and why you may not need to worry right away!

How Do Betta Fish Get Tumors?

If your betta fish has a tumor, you may not need to feel guilty that it’s something you’ve done.

In a lot of cases, betta fish are simply predisposed to tumors. There’s not a lot you could’ve done to stop it and it was just going to happen regardless.

However, they can be caused by other things as well. Letting carcinogenic’s into your tank, feeding them poor food, and viral infections caused by poor water conditions can also increase the chances of a tumor.

Tumors in bettas present as a lump under their skin. While it’s almost impossible to operate on, tumors don’t mean the end for your betta. Bettas can survive for months with a tumor. The best prevention measure is using a reputable breeder, as well as improving food and water quality.

(Check out this article on every disease and illness bettas can get! If you’re not sure whether it’s a tumor or not, this article will help you out!)

How Likely Is It Your Betta Will Get A Tumor?

If you’re not sure your betta has a tumor, you might be worrying now about them getting one. But don’t panic just yet! Tumors are actually quite rare in bettas. Out of all the illnesses your betta can suffer from, tumors are very far down the list.

If you think your betta has a tumor remember it could be something else. Ulcers and abscesses can look similar to tumors for example.

As well as ulcers and abscesses, a “tumor” could also be lumps caused by swim bladder disease, constipation, and fluid retention!

What Are The Symptoms Of Tumors In A Betta Fish?

If your betta is suffering from a tumor there’s going to be one big symptom. And that’s a lump! The size of the lump can vary, sometimes their small and sometimes they’re huge.

Sometimes you may not even be aware your betta has a tumor if they’re internal.

As well as noticing a lump you may also notice that they don’t seem as active anymore, they’ve stopped eating, and they’re having trouble swimming.

Once again though, remember, it’s far more likely this is being caused by another kind of illness.

What If Your Betta Fish Has A White Tumor

A lot of people notice that their betta fish’s tumor is white. If this is the case, then it might not be a tumor at all.

It Might Be An Abscess

In these circumstances, it could be an abscess. If it’s an abscess it’s going to be filled with pus. Over time it might even burst.

If it does burst, then you’re going to need to make sure you move your betta out of his tank if he’s with other fish.

When it bursts he’s going to have a large sore, so you’ll have to be extra careful, give him frequent water changes and make sure the tank conditions are perfect.

In a lot of cases, the abscess does so much damage that your betta will die However, it’s not uncommon for them to survive an abscess (depending on the size).

It Might Be An Ulcer

As well as being an abscess it could also be an ulcer. If it is an ulcer, you may notice that it’s red around the edges and looks sore. Your betta may also seem more emaciated and lethargic as well.

Where Can Tumors Be Located?

Tumors can be located all over your bettas body. However, depending on the area they might not be a tumor at all but something else. Here are the most common places people spot tumors on their betta fish.

Tumor On Your Betta Fish’ Head

One place that people tend to notice a tumor is on their bettas head. And while in a lot of cases it may be a tumor, it may also not be.

As well as being a tumor, a lump on your bettas head could also be a sign of a bacterial infection.

Columnaris is one such infection that occasionally causes this to happen. If you’re not sure whether it’s columnaris check out this article to find out more about the infection.

As well as a bacterial infection, it could also be a parasitical one.

And of course, in some cases, it is going to be a tumor on your bettas head.

Tumor On Your Betta Fish’s Side

As well as being on their head, you may notice a lump on your betta’s side. Once again, while this could be a tumor, it may not be.

In fact, when it comes to your betta fish’s side, there can be quite a few different causes of a lump coming out. Some of them are a lot more common than tumors, and also a lot more treatable!

It Might Be Swim Bladder Disease

As well as being a tumor, a lump could be a sign of swim bladder disease. If you notice your betta is having trouble staying buoyant, is lethargic, doesn’t eat, and in some cases has a curved spine, then the chances are its swim bladder disease.


It might also be dropsy. Unfortunately, if it is dropsy, you’re going to have a hard time saving your betta. In fact, a betta can survive a long time with a tumor, but when dropsy becomes too severe, they’re likely to die in a couple of days.

If it’s dropsy you’ll also notice that your betta seems bloated, has a curved spine and in the last stages pinecone scales.

A Bacterial Infection

And lastly, bacterial infections can sometimes cause lumps to appear on your bettas side. If you notice other fish in the tank getting sick or common symptoms of illness you may want to start treating your betta’s water with medication for bacteria.

Tumor On Betta Fish’s Stomach

Lastly, another commonplace for tumors to occur is on your betta’s stomach. If you do notice a lump then it may be a tumor, but that’s not always the case. As well as a tumor it could be dropsy, swim bladder disease, a bacterial infection, or even constipation!


If you notice a lump on your betta’s stomach then it could be constipation. The truth is, bettas are extremely gutty fish, so the chances of them getting constipated are quite common (And quite treatable.)

Constipation will also have other symptoms. Such as the inability to poop, not eating, bloating, lethargy and even swim bladder disease.

Tumor In Your Betta Fish’ Gills

When a tumor is noticeable on your bettas gill it’s often gill hyperplasia. Gill hyperplasia normally occurs when the gills have been damaged. This could be by a physical injury, parasitical or bacterial infection, or by toxins (like ammonia, nitrates, and nitrites.)

Instead of healing effectively, the gill tissue normally grows over the damaged area. This new skin forms a bump which can look like a tumor. Over time, the more the skin grows, the bigger the lump might become.

If the hyperplasia is severe, the chances are your bettas gill will stay like that. However, if it’s not too bad, they can sometimes go back to normal.

While these are common places for your betta to have a tumor, anywhere on their body is susceptible to tumors.

How Do You Treat Tumors In Betta Fish?

To be honest, there’s no real cure for tumors in betta fish. If you notice your betta has a tumor it’s time to think about their quality of life. If you think they’re still swimming around fine then you should let them live.

However, if they seem in pain all the time, it may be time to euthanize them.

In some cases, people have had their betta fish operated on successfully, however, the chances are it’s not likely to work, and may cause unnecessary suffering to your betta.

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How Do You Prevent Tumors In Bettas?

As previously mentioned, the biggest factor that determines whether your betta will suffer from a tumor is their genetics. However, here are some things you can do to reduce the chances.

Buy From Reputable Breeders

One thing you can do if you plan on getting a new betta is buying from a reputable breeder. Some fish companies inbreed their fish because it’s cheaper than importing them or breeding them properly.

As you can imagine, inbred fish are likely to suffer from a whole range of problems. And an increased chance of tumors is one of them.

Keep The Water Clean

You should also make sure you’re keeping the tank water clean. Clean water is going to reduce the risk of your betta becoming sick in general. And in the case of gill hyperplasia, it’s going to keep the ammonia levels low.

Feed Them High-Quality Food

Also, make sure you’re not feeding them cheap and low-quality food. We already know that in humans, dogs, and cats, poor food equals poor health. In fact, numerous times low-quality food has been proven to increase the risk of cancer in people.

And it’s no different with your betta. Make sure you’re feeding your betta high-quality food all the time and keep their diet varied as well! If you’re not sure what food to feed your betta, here’s an article that guides you through all the best foods for bettas!

Treat Other Infections Quickly

If your betta does become sick, make sure you’re treating it as soon as possible. If your betta has a weakened immune system they’re going to be more likely to catch a lot more sicknesses.

And the reduced strength of their immune system isn’t going to be good either. Once again this especially the case when you’re trying to stop a betta from getting gill hyperplasia.

Keep Carcinogenic’s Out Of The Water

Lastly, make sure you’re keeping carcinogenic’s out of the water and away from the tank. they’re going to be a big cause in tumors in your betta, so don’t let them near him!

A Tumor Doesn’t Mean The End

When you notice that your betta has a tumor, it doesn’t mean it’s the end. Lots of people have found that their bettas have lived full lives even with a tumor!

Maybe they’ll pass, but maybe they won’t. It can be hard to tell how long they’ll live. As long as they seem happy and as healthy as they can be, it might not be time to worry.

Euthanizing Your Betta When Their Tumor Is Too Much

However, there are some times when it’s time to let your betta go. If you think they’re in pain and they’re not happy anymore then it may be time to euthanize them.

You may have heard that clove oil and alcohol are two ways to do it, however, they’re not recommended. Alcohol will burn your bettas gills and insides until he dies and cloves oil can be hard to measure accurately.

Instead, you should use MS-222 which is also known as Fin-quel. It’s the most effective way to euthanize your betta.

However, before you consider euthanization make sure you speak to a vet!

When Should You Euthanize Your Betta?

If your betta gets a tumor that can’t be treated, sometimes the only kind thing to do is to put them to sleep in a humane way. It’s never an easy decision, and even if you’ve done everything you can to treat the tumors, it is heartbreaking to see your little fish suffering in their tank. If that’s the case, do the right thing and put them down in the most compassionate way possible.

How Likely Is It Your Betta Will Get A Tumor?

It’s tough to predict the odds of your betta getting a tumor since it can be affected by lots of things like a bad diet, dirty water, viruses, and genetics. Tumors don’t happen too often in betta fish, but they’re definitely a possibility, especially as they get older.


Now you know what to do when your betta fish has a tumor. Unfortunately, it’s sometimes a hard part of owning a betta, yet you still need to make sure you do the best you can.

If you want to know everything about betta fish care, click here!

Here are a few things to remember.

  • The tumor could be an abscess, ulcer, swim bladder disease, constipation, dropsy, a bacterial infection, or parasitical infection
  • A tumor in your bettas gills is much more likely to be gill hyperplasia.
  • To avoid tumors in your betta make sure you feed them high-quality food, keep the water clean, buy from reputable sellers and avoid carcinogens getting into the tank.
  • There’s no real treatment for tumors and it’s more about keeping them comfortable for as long as possible.
  • If you’re going to euthanize your betta make sure you avoid using cloves oil and alcohol.
Ultimate Betta Fish Care Guide
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Hey! I'm Nicolas from Iguane Media !

Blogger and Owner of the betta care fish guide
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10 thoughts on “Betta Fish Tumors: Why They Happen & What To Do”

  1. I have a betta. It had a growth/lump on the top part of it’s fin. almost was like a little bubble floating on it.
    Anyways it was there last night but went away by morning. Was kinda shocking because of the size of it. About the size of the eye, but now you wouldn’t even know if it had one. We did remove a toy that we added in so it might have been some allergies.

    • It’s great to hear the lump went down! But you should keep an eye on the area for the next couple of weeks to look for any changes.

  2. I have a betta fish for a couple of months.. My fish’s tumor has been growth and is now huge. He also has a second one growing at his side. I want to help him, but I dont know how. I have read a lot of articles. Watched a lot of videos. He dont wanna eat, but he swim around. The tumor is not affecting his swimming. Any suggestions?

    • Asides from taking them to a professional, there’s not much you can do now except keep him comfortable. And even though he has a tumor, he may still live for a couple more years.

  3. My betta has had a tumor for 5 months now, he is still active. I’m glad after reading your article that my boy might live a longer life than I thought even with the tumor! I now know that I need to clean his tank more often. I keep wondering sometimes though, the lump is small some days and big other days, what’s up with that?

    • That is bizarre that it changes sizes regularly, it’s best just to keep an eye on it and make sure it’s not getting any worse.

  4. My betta has a lump. How would I treat constipation, if that is the problem? The water is clean and food is Betta Bio-gold.

  5. My betta has a large lump near his tail. It’s raised and almost looks like a “saddle”. A small portion has come off and it is white. He doesn’t seem to be in pain and swims fine along with eating. What do you suggest would be proper treatment? Thanks.


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