Betta Fish Tumor: Causes, Symptoms, Treatments, and Prevention

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For betta fish owners, taking good care of their lively and colorful pet is a responsibility that brings joy. One of the scariest experiences I have come across as a Betta Fish owner is seeing my elderly Betta with a white growth on their body.

This is a tumor on your fish. I have been in your shoes before and know how helpless the feeling is when you first see this – and how difficult it is to find someone who can operate on your fish. Knowing more about this health issue can help you maintain your betta’s overall well being, maybe even cure it, or give you comfort on how to enjoy the rest of the time you have with your Betta.

Key Takeaways

  • Recognize the signs of tumors in betta fish & know how to differentiate between different types.
  • Treatments for external/internal tumors vary and may involve surgery, medication, or quarantine.
  • Preventive strategies include maintaining good water quality, providing a balanced diet & seeking advice from an experienced vet.

How To Recognize A Betta Fish Tumor

It is important for a betta fish owner to be able to recognize the symptoms of tumors in their pet. Betta fish can develop external and internal growths, which appear differently depending on size, area, and other factors. Identifying them quickly will make treatment more successful.

To detect whether there are any lumps or changes in behavior, we should take into account when caring for our beloved betta fish. We will discuss both external and internal tumors and how they are different.

External Types


Betta fish that are healthy typically will not have any visible abnormalities such as lumps or bumps on the scales. Tumors in betta fish can occur and manifest externally. The most frequent causes include abdominal cancerous growths, lumpy lesions resulting from bacterial infections, and a type of abnormal tissue overgrowth called gill hyperplasia1, which leads to tumor-like bulges appearing on their gills.

External tumors can appear in various parts of your Betta’s body, including:

  • The sides of the betta fish’s body
  • Fins and tail
  • Belly
  • On the gills
  • On their head

The common tumors you will come across will be external. Betta fish tumor symptoms aside from the obvious growth are lack of appetite and slowing down of activity. The fish may also become blind as a result.

Internal Types

Internal tumors can be a major issue for betta fish, as they tend to develop inside the body and are more difficult to detect. This condition is due to physical damage, bacterial infections, parasites or toxins in aquarium water causing tumor like growths. Unfortunately, internal tumors or damage are harder to cure and often are subject to euthanization.

Often times internal tumor are not actually tumors themselves but are a result of conditions such as bloating, dropsy, or bacterial infections.


Betta fish can develop tumors and understanding the possible causes of this issue can help in both prevention and treatment. Genetic traits, poor dieting habits, unsanitary water conditions as well as viral infections are contributing factors that could be involved in how these fish get cancerous growths.

The risk of developing such a condition is lowered when taking measures to ensure proper nutrition for betta fish. Feed them high-quality products containing all essential nutrients needed for immunity protection. Unhygienic environments should also not be tolerated, so it’s important to keep tanks clean with regular water changes being done regularly.

My Personal Experience

In my experience, I will say that fancier varieties of Betta fish are more prone to tumors than Plakat bettas. I believe this has more to do with all the experimentation that betta breeder do to get the specific breed of fish they sell you and also a combination of not screening their stock well before sale. Most tumors will not appear on a fish later in adult life, leading to the breeder being unable to resolve the issue, so the cycle repeats itself, especially if the fish is bred.

There is no environmental factor or equipment that I would consider that causes tumors to appear more than others (with the exception of Formalin – but most do not use this unless as a last resort). This is me speaking with 25 years of experience and running multiple fish stores in the past. I frequently notice over the years that it is fancier style bettas and koi bettas that experience this more. If you want to decrease your risk, I would recommend that you seek out plakats and avoid plakat koi bettas.

Benign Or Cancerous

When it comes to betta fish, there are two types of tumors they can develop. Benign and cancerous. Benign growths typically don’t spread throughout the body but instead require medication or surgery as treatment methods. On the other hand, a cancerous tumor is much more severe in its effects – reaching other parts of the body and eventually killing the fish.

It’s critical to be able to identify which kind of tumorous issue your betta fish may possess so that you understand how best to treat them accordingly. Benign tumors can be removed with the assistance of a veterinarian.

I know that veterinarians are hard to find in this hobby, so if you can’t find one, try to find an experienced hobbyist who knows what to do and live with the fact that amateur surgery could result in the death of the fish. It’s up to you if you want to take this risk.

I’ve tried with other conditions before, like with swim bladder disease. I don’t have vets around me who can take care of these conditions. Even with my experience, my success rate isn’t that great. It’s not always the condition itself but the stress of the procedure. When I was new to this, I didn’t use solutions like clove oil to knock out my fish. Learn from my mistakes and talk to hobbyists who are offering to do this for you!


Unfortunately, if a tumor is identified, there isn’t much you can do, and it’s best for you to address quality of life issues to maximize the comfort of your fish. There are no home remedies that will cure cancerous tumors in betta fish. For those of you lucky enough to have a vet around you, surgical removal is the best way to address this problem. I have a wonderful video in the next section showing you one of the rare Vets in our space who does this procedure.

Surgical Removal

The best betta fish tumor treatment is removing the tumor itself. However, it is an uncertain process with no guarantees of success. It would be best to seek the assistance of a knowledgeable veterinarian experienced in treating tropical fish for such procedures. The following video describes this process in detail. Note the fish is knocked out to prevent stress from the procedure. The fish is also revived carefully by The Fish Doctor. View this video in detail before attempting this with a Vet or with an experienced hobbyist. Note success is not guaranteed.

Common Non-Tumor Lumps

Betta fish can develop lumps for different reasons that aren’t always tumor related. Abscesses, ulcers, swim bladder disease, dropsy, and constipation are some of the most common causes of these growths on betta fish bodies. Let’s talk about these other conditions that could occur and should be evaluated before considering the next steps:


If you see a large white growth on your betta fish, this is likely an abscess due to a loss of scales that has developed into a bacterial infection. This is typically caused by injuries – either from other fish, running into decorations, or being sucked up by a filter. While most injuries should heal on their own, this large white growth is a troublesome sign.

A betta fish abscess if left untreated, will rupture and cause further damage. It should be treated as a bacterial infection, and you should use antibiotics to treat the condition.

Fungal Infections

A white cotton like growth would indicate a fungal infection not a tumor. Those should be treated with anti-fungal medication and typically have good outcomes with treatment.


Columnaris is shown as red marks or growths. It is a bacterial infection that oftentimes will kill a fish. Immediate antibacterial care should be taken ASAP.


Parasites can cause bloating or flattening of a belly. This is usually caused by rings or internal parasites, both of which can be cleared with a medication mix of Seachem Focus and General Cure by feeding the affected fish food treated with these two products.

API General Cure

A great general medication for various fish diseases. Can be used in water or fed direct with a binder like SeaChem Focus.

Buy On Amazon Buy On Chewy

Swim Bladder Disease

Swim bladder disease is usually caused by bacterial or parasite infections. Fish suffering from swim bladder disease may experience bump formations because it interferes with their kidney functioning, resulting in fluid retention issues, which manifest through protrusions all over them. They are usually caused by overfeeding, poor temperature stability, or breeding defects.


Dropsy has similar effects since its cause lies within buildups around the body’s cells making scales pop out more than usual due to the bloating processes. A betta fish develops dropsy due to poor water, stress, water temperature instability, and parasites.

Prevention Strategies

Reducing the risk of a tumor on your betta fish developing is a great step and should start before a purchase. Purchasing from a reliable breeder or local store is recommended. Inbred fishes and those coming from poor stock have an increased chance of having health issues like lumps so it’s important that only good quality be chosen.

Providing well balanced diets with keep a healthy fish while regular water changes along with efficient filtration systems need to be implemented along with a low stress environment. Daily checkups are also encouraged as this will allow suspicious activities such as tumors on bodies at early stages to better manage its progress ahead than later times when something unexpected happens already making potential risks hard (or even impossible)to limit if left unchecked longer.

Should I Euthanize?

To euthanize your betta fish is a stressful and heartbreaking decision. Euthanization should be considered if you cannot get an operation and if the stages are advanced. You can euthanize the fish with clove oil, which we have the procedure outlined in our blog post here.

Frequently Asked Questions

How do I know if my fish has a tumor?

External growths in fish can often be identified by feeling for bumps or lumps under the skin. Internal tumors, are harder to detect and are typically fatal. If your fish has a swollen abdomen, it may indicate that they have an internal tumor, which should warrant investigation.

Why does my betta fish have a white bump?

Your betta fish is most likely affected by an external parasitic infection called ick, causing a white bump to appear. This parasite will remain attached for four or five days until it drops off and then attaches itself once more. If the bump is large and raised, this could indicate a bigger issue like a bacterial infection or tumor.

What is the common cause of betta fish death?

The most common explanations for the death of betta fish are issues such as poor water conditions, providing too much food, and having temperatures that are too cool in their habitat, all factors that can harm them physically and create stress levels leading to sickness or demise.

How do you treat betta fish tumors?

For a great majority of tumors and cancers detected in fish, no treatment or cure exists. When discovered early on and the tumor is external, the tumor can be removed with the help of a veterinarian.

How can I differentiate between benign and cancerous tumors?

Benign tumors don’t invade other areas and are simpler to manage than cancerous ones, which can spread.

Closing Thoughts

It is essential for betta fish owners to be aware of the potential issues associated with tumors in their beloved pets. Taking proactive steps such as providing a proper diet and clean tank environment, monitoring your pet’s health daily, and taking prompt action can go far in minimizing any risks related to tumor formation. Catching any warning signs at an early stage is key if effective treatment needs to take place.

Betta fish provide wonderful companionship that should not be taken lightly. It is the owner’s responsibility to ensure they remain healthy and happy through constant caretaking efforts. Always do what’s best for your Betta fish. Let me know if you have any comments to share below, and I’ll be here to answer.

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