Can Goldfish Get Cancer? {Causes, Symptoms, and Treatment}

Is your goldfish unwell and you think they might have cancer? Can goldfish get cancer?

Do they get cancer like us? Is there anything we can do for them?

I will cover all you need to know below.

Can Goldfish Get Cancer?

Yes, goldfish can get cancer. While it may seem like a small problem, understanding cancers and cancerous tumors in goldfish is crucial for their overall health and well-being.

Many owners of fishes, including goldfish and koi, have questions about the ability of their fish to develop cancerous tumors. While mild cases of diseases are common in female koi, male koi, as well as goldfish, can also be affected.

There are several misconceptions about goldfish and cancer that we will address throughout this post, including the popular belief that kona are immune to cancer.

Can Goldfish Get Cancer

As an owner, it’s important to know how to recognize signs of cancers in your fishes and what steps you can take to prevent or treat the problem. We will discuss ways to maintain the quality of life for your fishes and provide tips on how to keep them healthy.

Causes of Tumors and Growths on Goldfish

Factors that Contribute to Tumor Growth in Goldfish

Goldfish can develop tumors, which are abnormal cell growths that form lumps or bumps on their bodies. While it is not entirely clear what causes tumors in goldfish, there is limited information available on the topic. Several factors can contribute to their development, including poor water quality.

When the water in a goldfish tank is not properly maintained, it can become contaminated with harmful bacteria, viruses, and other pathogens that can weaken the fish’s immune system. This weakened immunity can make it easier for tumors to form.

Another factor that may contribute to tumor growth in goldfish is genetics. Some breeds of goldfish are more prone to developing tumors than others due to genetic abnormalities or mutations. This information can be helpful in identifying the potential risks of certain goldfish breeds.

Environmental Causes such as Water Quality, Temperature, etc.

As mentioned earlier, information on poor water quality is crucial in understanding the leading environmental causes of tumor growth in goldfish. To prevent this from happening, it’s important to keep your fish tank clean by performing regular water changes and using a high-quality filter system.

Information on temperature fluctuations can also be a contributing factor to tumor growth in goldfish. If there is not enough information on how to maintain a stable temperature in your fish tank, or if you are not aware of the potential dangers of temperature fluctuations, it can cause stress on your fish’s body and weaken its immune system.

Other environmental factors that could contribute to tumor growth include inadequate nutrition or exposure to toxins like ammonia or nitrite. It is important to gather more information on these factors to better understand their impact on tumor development.

Genetic Factors That May Increase Susceptibility to Tumor Growths

While some breeds of goldfish are more prone to developing tumors than others due to genetic abnormalities or mutations, any breed of goldfish has the potential for tumor growth. However, certain genetic traits may increase susceptibility.

For example, some strains of fancy goldfish have been selectively bred to have shorter bodies and more rounded heads.

Preventing Tumors in Goldfish

Goldfish are prone to developing tumors, just like any other living creature. These tumors can be benign or cancerous, but they are generally caused by environmental factors such as poor water quality, inadequate nutrition, and stress.

Steps to Reduce the Risk of Tumor Development

To help prevent tumor development in your pet fish, there are several steps you can take:

  1. Maintain a healthy environment for your fish by regularly cleaning their tank or pond. This includes changing the water frequently and ensuring that the temperature and pH levels are appropriate for your fish.
  2. Choose appropriate food sources for your fish. A balanced diet with high-quality food will help keep your fish healthy and reduce the risk of tumor development.
  3. Avoid overfeeding your fish, as this can lead to obesity and other health issues that may increase the risk of tumor development.
  4. Consider adding plants or other decorations to your fish’s environment to reduce stress levels.
  5. Regularly check on your fish’s overall health and look for any signs of abnormal growths or behavior.

Types of Tumors in Goldfish

Goldfish, koi fishes, are a popular pet fish, but just like any other living creature, they can get sick and develop diseases. One common question among goldfish and koi owners is whether their fish can get cancer. The answer is yes; goldfish and koi fishes can develop tumors that may or may not be cancerous cancers.

There is information on several types of tumors that can be a problem and affect goldfish, including cancers and disease.


A benign tumor that appears as a small white bump on the skin or fins. For more information on this disease, including protocol for diagnosis and treatment of papillomas and other cancers, please consult with a medical professional.


A benign tumor that grows from the connective tissue and appears as a firm lump under the skin. For more information on fibroma, consult your healthcare provider.


A benign tumor made up of fat cells that appear as soft lumps under the skin. For more information on lipomas, consult your healthcare provider.


A malignant tumor that affects pigment cells and appears as dark spots on the skin or fins. For more information on melanoma, consult a medical professional.

Handling and Treating Tumors and Growths in Goldfish

If you’re a goldfish owner, it’s important to know that like any other living creature, goldfish can develop tumors. While not all tumors are cancerous, they can still cause problems for your fish if left untreated.

Identifying Different Types of Tumor Growths

There are several different types of tumors that can affect goldfish. The most common ones include:

  • External tumors: These grow on the outside of the fish’s body and are usually visible as lumps or bumps.
  • Internal tumors: These grow inside the fish’s body and may not be visible until they become large enough to cause problems.
  • Skin tumors: These grow on the skin tissue of the fish.
  • Gill tumors: These grow on or near the gills of the fish.

To identify whether your goldfish has a tumor growth, look out for these signs:

  • Lumps or bumps on their body
  • Changes in behavior such as lethargy or loss of appetite
  • Changes in coloration
  • Difficulty swimming or breathing

If you notice any of these symptoms, take your fish to a veterinarian who specializes in aquatic animals immediately.

Safe Handling Procedures When Dealing with Sick or Injured Fish

When dealing with sick or injured fish, it’s important to handle them with care to avoid causing further harm. Here are some safe handling procedures you should follow:

  1. Use a net to gently remove your fish from its tank.
  2. Place your fish in a clean container filled with water from its original tank.
  3. Avoid touching your fish with bare hands as this can damage its delicate skin.

Understanding and Preventing Tumors in Goldfish

In conclusion, goldfish can indeed get tumors, and it’s essential to understand the types of tumors and their symptoms. Nerve sheath tumors are common in goldfish, but other types can also occur. Identifying the causes of tumors and growths on pet fish is crucial for their care, and prevention is always better than treatment. To prevent tumors in pet fish, maintain a clean tank environment, provide a balanced diet, avoid overcrowding the tank, and perform regular check-ups.

Remember that taking care of your pet fish’s health is crucial to ensure they live a long and healthy life. By understanding how to identify the signs of tumors in goldfish and taking preventative measures, you can help keep your pet fish healthy.


Q: Can I prevent all types of tumors in my goldfish?

A: While some types of tumors may be prevented through proper care and maintenance, others may be genetic or caused by unknown factors.

Q: How do I know if my goldfish has a tumor?

A: Look for any unusual lumps or bumps on your goldfish’s body or changes in behavior such as lethargy or loss of appetite.

Q: What should I do if I suspect my goldfish has a tumor?

A: Consult with a veterinarian who specializes in aquatic animals for proper diagnosis and treatment options.

Q: Is there anything I can do to treat my goldfish’s tumor at home?

A: It’s best to consult with a veterinarian for proper treatment options as attempting to treat at home could potentially harm your pet fish.

Q: Can stress cause tumors in goldfish?

A: While stress can weaken an animal’s immune system making them more susceptible to disease and illness, there is no direct correlation between stress and tumor development.

Q: Are certain breeds of goldfish more prone to developing tumors?

A: Some breeds of goldfish, such as the Lionhead or Oranda, may be more prone to developing tumors due to their genetic makeup.

Q: Can tumors in goldfish be cancerous and spread to other fish?

A: While some tumors in goldfish can be cancerous, they typically do not spread to other fish and are not contagious.


Hello, I'm Jason. I'm the guy behind I volunteer at my local fish shop and I created this site to offer tips and advice on the fish I care for.