Betta Fish Tumor: Symptoms, Causes & Treatment (Full Guide)

Last Updated: May 26, 2022 by Dave Gibbins

A tumor on Betta fish is often a sign of underlying health issues that you, as a fishkeeper, need to address quickly. A common cause for a Betta fish tumor is cancerous cells. In some cases, however, the white tumor-like growth indicates an abscess or an ulcer. 

Why does a tumor form? Can you treat the water or the tumor itself to improve surviving a Betta fish tumor? Let’s look at the tumor, the symptoms it produces, and possible treatments for it.

We believe one of the best lines of defense is an educated keeper. Knowledge will improve the quality of your pet’s life and the enjoyment of your hobby!

How Likely Is It That A Tumor Will Grow On Your Betta Fish?

A tumor on Betta fish is a rare occurrence. Several diseases or injuries are more likely to affect your pet. If you notice something that looks like a tumor, it could be symptoms of something else entirely.

Swim bladder disease, constipation, even fluid retention can create swelling or bumps that appear similar to a Betta fish tumor. Bacterial infections can cause your Betta to develop an abscess or ulcer (fungal infections usually cause discolorization or growths that appear like cotton).

Aquariums with unhealthy water conditions and aggressive tank-mates that bite will also produce symptoms that look like a tumor.

How Do You Know If Your Betta Fish Has A Tumor?

Bumps and spots can be a Betta fish tumor. They can be just under the surface, causing lumps. They can also grow on the outer scales of your pet or on internal organs and tissues.

A tumor on Betta fish can vary in size and location on the fish (including on the tail, on side scales, a tumor on head scales (interorbital region), or internal (such as a brain tumor). Smaller growths may not affect your pet much, but a larger tumor can make it difficult for your Betta fish to swim through the water.

Betta fish white tumor

There are times that a tumor on a Betta fish is not a cancerous growth. More often, these tumor growths from Betta fish turning white can indicate:

• Abcesses
• Ulcers
• Other conditions

An abscess that appears to be a tumor

The white tumor you see on your fish is likely an abscess caused by a bacterial infection more so than cancerous tumor growth.

Fungal infections usually cause scale discolorization. External tumor shapes caused by bacterial infections have a solid appearance, whereas growths caused by fungal infections often appear porous, like cotton.

The ‘white tumor’ caused by bacterial infections begins from an exterior injury. They are caused by bumps during water changes, tank cleaning, aggressive tank mates, or self-inflicted while rubbing on objects.

An abscess heals over time, but dirty water can cause bacteria to enter the wound. Untreated, they grow until they burst, leaving a large hole on side scales or tattered fins.

An ulcer that appears to be a tumor on Betta fish

Another common white tumor-like injury is an ulcer. These grow into open wounds but often begin as a lump with red discolorization around it. A breakdown in your pet’s immune system is often the start of an ulcer.

The damage from those open wounds can cause permanent scale loss. Ulcers are also a pathway for bacterial or fungal infections to enter your Betta’s body.

Minor bacterial or fungal infections will usually clear up with a water change (or eliminating other potential hazards in the water column). More advanced infections will require antibiotic medicines placed in the water of the aquarium or a hospital tank.

Other conditions that resemble a Betta fish tumor

A side-effect of Columnaris can be tumor-like bumps around and on the head scales. Bacterial growth or parasites such as those resulting to Betta velvet can also cause abscesses on the Betta fish’s head.

Frequent water changes and medicines can eliminate these problems. Cancerous Betta fish tumor on head scales is a fatal diagnosis; nothing can be done to remove a tumor without distressing the fish so badly that you end up with a dead Betta while trying.

Bacterial infections can produce Betta fish tumors-like lumps on the side scales. Swim bladder disease is also a known cause for looking like Betta fish tumors on side scales or belly.

You should treat bacterial growths that will not disappear on their own. Tumor shapes or lumps caused by swim bladder disease can often be treated by withholding food portions to decrease the swelling.

Constipation can cause lumps that appear as internal tumors, or it can contribute to swimming bladder disease. Stop feeding your pet, and the bloating that looks like a Betta fish tumor will shrink.

A tumor on Betta fish gills can form due to Gill Hyperplasia. The cause of the swelling “tumor” appearance is damage to the gill structure, which usually heals and shrinks over time. Severe gill damage can make the tumors permanent.

Tumor-like lumps on Betta fish tail fins occur when swelling or bacterial growth from other fish nipping at your Betta damage it. These will usually shrink over time, but some damage may require applied treatments.

Betta Fish Tumor Symptoms

The only real sign of a Betta fish tumor is swelling or a lump. Brain tumors and other internal growth will be harder to detect in the early stages like an external tumor is. Internal tumors usually become visible as swelling causes portions of the body to grow.

Other symptoms that can indicate a possible tumor include:

• Loss of appetite
• Becoming lethargic
• Difficulty with balance or swimming

A loss of appetite, along with tumor growth, can indicate several problems, as mentioned previously (see “white tumor” above). A lack of eating does go with cancerous tumor growth, though.

You will notice that your fish does not eat aggressively, if at all. If it does nibble, most of the food will remain in the water column or float down to the substrate.

Another indicator of your Betta’s health is its activity. Unusual patterns of lethargy can indicate a problem. Combine this with a growing tumor, and you need to address the situation quickly.

The best thing you can do here is to eliminate any stress sources and perform water changes to provide a clean environment. That can remove potential problems that are not cancerous while preparing the aquarium for future treatment.

Having issues with staying upright or irregular swimming through the water often manifests with internal tumors. The growth causes problems with other organs in your pet. Skipping feeding can eliminate constipation or other issues, allowing you to diagnose the lumps more accurately.

How To Treat A Tumor In Betta Fish

Presently, there is very little that you can do as a fish keeper if your Betta develops a cancerous tumor.

Some veterinarians can perform operations to remove a tumor. These Betta fish tumor treatment procedures are invasive, with low success rates. Even successfully removed tumors can grow back.

A few tumor locations are treatable. A gill tumor caused by thyroid issues is treatable with medication in the water.

Internal tumors are usually not noticed until it is too late. A Betta fish tumor that does not affect how your pet breaths, eats, or swims, can be left alone. You may want to consider other options if your pet is suffering, however.

Can You Prevent A Betta Fish Tumor In The First Place?

Keep in mind that some Betta fish are prone to cancerous growth due to genetic disposition. Environmental factors that you may not be aware of can also cause a Betta fish to form tumors later in its life.

There are some things that you, as a fish keeper, can do that will lessen the chance of Betta fish tumor development:

• Purchase fish from reputable dealers
• Keep optimal water conditions
• Offer a healthy diet
• Treat other diseases quickly

Buying your pets from reputable dealers can avoid a lot of health problems. Many chain stores use breeders with severely inbred stock. The genetic makeup of the fish can influence its health, including susceptibility to cancerous tumors.

A reliable filtration system promotes healthy bacterial colonies while eliminating poisons from the water column. Frequent changes of about 25-percent of the fish tank’s water will also keep the conditions optimal. Water quality will help fish stay healthy, or it will make them sick.

Like humans, your Betta needs a balanced diet that offers the right combination of plant-based matter and animal protein. Proper portions prevent constipation and polluted fish tanks. A healthy diet will keep your Betta’s immune system running at its best, preventing many bacterial and fungal infections that lead to tumor-like growths.

Your fish is likely to get sick at some point, no matter how well you maintain it and its aquarium. Watch daily for problems with the water conditions or with the Betta itself. Once you identify a problem, treat your pet quickly to prevent it from becoming more serious.

Your Prevention Today Keeps The Tumor Away

Cancer is as devastating to your Betta fish as it is to anything else. Currently, Betta fish tumor treatment is limited, with operations offering minimal success.

Fortunately, many growths and lumps you might find on your Betta fish are not white tumors. These lumps are the results of an abscess or ulcer more than they are of cancer. Interior diseases and infections can also cause lumps, but these things are usually treatable if caught early.

Buying healthy stock, feeding it a healthy diet in a clean environment, and addressing concerns as they pop up, will help you keep Betta happy that live a long life.

Do you have any questions or comments? Make sure to leave them below to be answered. They can also help start a conversation that covers something you want to explore further!