Betta Fish Tumour: Symptoms, Treatment, Prevention

Betta Fish tumour symptoms treatment prevention
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Betta fish are a low-maintenance pet that brings lots of joy and excitement to your life with their stunning colours and flowy fins.

However, they need your full-time care as they’re susceptible to developing various health conditions just like other animals.

Most of these conditions are easily curable, while others require special treatments.

Tumour is one of these conditions that can affect your bettas.

If you notice a tumour-like growth protruding from your betta’s body, it might be a tumour symptom.

In this guide, you’ll learn how to identify betta fish tumours, the potential causes and symptoms of this disease, and what treatments you can apply to save your betta’s life.

In the end, we’ll also discuss some preventative measures to prevent this disease from affecting your fish.

What is a betta fish tumour?

Like other animals, betta fish can develop abnormal growths or masses of cells in their body, called tumours.

They can be benign or malignant and occur in different body parts of fish, especially fins, heads, and internal organs.

In most cases, tumours are large enough to be easily noticeable from outside of the fish’s skin in the form of bumps or lumps.

However, tumours can also be tiny and located internally in your betta’s body, making them unnoticeable to the naked eye.

Such tumours are challenging to treat and are likely to become lethal for the fish.

It’s also important to remember that not all tumours are cancerous; some may be common lumps or bumps that are easy to treat.

You must conduct an effective diagnosis to distinguish cancerous tumours from common lumps.

What causes tumours?

The exact cause of tumours in betta is unknown.

However, aquarists believe the following factors can be the potential causes of this disease:

  • Genetic issues

Some breeds of betta fish are genetically predisposed to developing tumours. Vulnerability to cancerous tumours due to genetic factors can pass from parents to the next generations in bettas.

If your betta is suffering from tumours due to genetic issues, there’s nothing much you can do to save them.

In fact, it might be better to cull them to prevent them from suffering in the future.

  • Poor water quality

Betta fish need clean and well-maintained water conditions to stay healthy and active.. Suppose the water is not clean and adequately maintained.

In that case, it can lead to the buildup of wastes, food leftover, ammonia, and other harmful toxins that can compromise the functionality of your bettas’ immune system, putting them at risk of tumour development.

  • Sudden changes in water parameters

Betta fish are extremely sensitive to changes in the parameters of their living environment.

Even a minor change in water temperature or pH can trigger stress in your fish, compromising their immunity against cancerous tumours.

A sudden change in the living conditions may shock your bettas, making them susceptible to tumours and other health conditions.

  • Ageing factor

Experts believe that the risk of developing cancerous tumours in betta fish increases with their age.

When betta fish start to get old, they may start losing the capability, capacity, and functionality of their immune system, increasing the risk of tumour development.

  • Stress

Stress negatively impacts your betta’s immune system.

A stressed betta can’t fight off tumours as actively as a healthy one. Your fish may become stressed due to various reasons, such as:

  • Inadequate space in the aquarium
  • Poor water conditions
  • Too high or low temperatures, or pH levels
  • Overcrowding
  • Aggressive tank mates

Chronic stress can weaken fish’s immune system, making them more susceptible to developing cancerous tumours and other diseases.

  • Physical injuries or infections

Betta fish suffering from physical injuries or bacterial/fungal infections may be more prone to developing tumours.

Internal tumours can be more likely to occur when the injuries or infections deeply affect the soft tissues of the fish’s body.

  • Low-quality diet

Low-quality diet is another stress-triggering factor in betta fish that can make them prone to tumour development.

Feeding a poor, unbalanced diet to betta fish can negatively affect their nutrition and ability to fight off conditions like tumours.

Symptoms of tumour in betta fish

Symptoms of tumours in betta fish can vary depending on their type (external or internal), location, and size, as well as the overall health of the fish.

Tumours can grow in any part of the fish’s body, so the appearance of symptoms may not be limited to a specific body area.

Some common symptoms that may indicate tumour development in betta fish include:

  • Noticeable lumps or tumour-like growths

One of the most apparent symptoms of an external tumour is a lump or tumour-like growth on the fish’s body.

This symptom is limited to external tumours only. You can quickly notice lumps or growths on your betta’s body with the naked eye.

  • Abnormal swimming patterns

If the tumours are large in size, covering most parts of your betta’s body, they may face difficulty swimming, which can show in the form of abnormal swimming patterns.

A betta suffering from tumours may swim slowly or lethargically. They may find it challenging to maintain their balance in the water.

  • Lethargy

Betta fish with tumours may show temporary inactivity and lethargic behaviour.

They may stick to a decoration or live plant in the aquarium and stay there for extended periods.

If your betta lacks interest in swimming and roaming around in the fish tank, it might indicate tumour development.

  • Breathing difficulties

In some cases, a tumour may grow in the fish’s respiratory system, making it difficult for them to breathe normally.

You may find bettas gasping on the water’s surface under such conditions. Breathing difficulties can be life-threatening for your betta fish, triggering hypoxia.

  • Anorexia (loss of appetite)

A betta fish with cancerous tumours may lose appetite or eat less than usual. However, loss of appetite in betta fish can also result from various other health conditions, so it’s not a conclusive symptom of a tumour.

  • Body discolouration

If you notice that your betta has lost body colour or developed rough patches in different body areas, it might be due to a tumour.

In some cases, the fish’s skin may become inflamed in addition to discolouration, especially in the area surrounding the tumour.

Among the abovementioned symptoms, breathing difficulties, lethargy, loss of appetite, and body discolouration can show up as the manifestations of both internal and external tumours.

The symptoms may also vary from fish to fish, so it’s essential to conduct regular diagnoses of your betta’s behaviour, appetite cycles, swimming patterns, and overall health conditions to identify tumours.

How to treat betta fish tumour

The treatment of betta fish tumours depends on the tumour’s size, type, severity, and location, which means internal and external tumours have different treatments.

You must be sure about the type and severity of the tumour in your betta before applying any treatment.

  • Surgical Procedure

Your veterinarian may recommend a surgical procedure to remove your betta’s tumour. However, surgery is often an extreme measure, and many choose to not do it for their fish.

Experts believe surgical procedures may be effective for removing benign tumours, while malignant tumours have no such effective treatment as they can regrow again after removal.

Another downside of surgery as a treatment for betta fish tumours is that it’s an expensive option.

  • Medication

Experts believe some tumours may respond to certain medications, such as antibiotics or anti-inflammatory drugs.

However, you must consult with your veterinarian or local fish store before using such medications.

  • Supportive care

Supportive care is more like a secondary treatment option that helps reduce the risk of further tumour development.

It helps you strengthen your bettas’ immune system so they can fight off both internal and external tumours.

In supportive care, you maintain a clean and stress-free environment for your betta fish to prevent them from becoming stressed out or shocked, which can compromise their immune system.

It’s important to keep in mind that not all tumours are treatable, particularly if they’re malignant or located in sensitive tissues or organs.

Treating non-cancerous tumours

As mentioned earlier, not all tumours need to be cancerous, as some may be merely bumps or lumps that can be treated easily.

Physical injuries can cause lumps in betta fish, a fight with aggressive tankmates, or body rubbing on sharp or rough objects in the aquarium.

Several health conditions such as ulcers, gill hyperplasia, parasites, constipation, dropsy, and swim bladder disease can also cause lumps in bettas.

Non-cancerous tumours can be treated through the following steps:

Step 1: Quarantining

If you suspect that your bettas have developed lumps or non-cancerous tumours, then isolate them from healthy fish and move them to a quarantine tank.

Ensure the quarantine tank has some water from the main aquarium to prevent bettas from becoming shocked.

Step 2: Maintain the optimum water parameters

Now that your bettas are quarantined, check the water parameters in the main aquarium.

The ideal water parameters include ammonia at 0 ppm, nitrite at 0 ppm, and nitrate at less than 20 ppm.

The water temperature and pH level should be in the acceptable range, depending on the species of your betta.

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Step 3: Medication

Medicate your bettas in a quarantine tank with an antibiotic or antifungal medication recommended by your veterinarian or local fish store.

You may also use aquarium salt as a medication as it’s believed to boost the capacity and capability of the fish’s immune system.

Besides these steps, regular water changes are also helpful to deal effectively with betta fish tumours as they allow you to maintain optimum water parameters in the aquarium.

How to prevent tumours in betta fish

You can prevent tumours in betta fish by taking the following preventative measures:

  • Keep the fish tank clean and well-maintained: Cleanliness and regular maintenance are extremely helpful against tumour development. You can use an efficient filtration system and perform regular water changes to maintain high water quality in the aquarium.
  • Maintain the water parameters at their optimum values: The temperature, pH level, nitrite level, ammonia level, and nitrate level of your aquarium’s water should be at their optimum values to avoid stress in your betta fish.
  • Avoid overcrowding: Overcrowding in the fish tank can lead to stress in your bettas and may trigger aggression in them, making them susceptible to weakness in the immune system.
  • Feed your betta a nutritious and balanced diet: A balanced and high-quality diet can boost the efficiency and strength of your betta’s immune system, reducing the risk of developing tumours.


Tumours in betta fish are difficult to treat unless you diagnose them early.

Therefore, it’s always better to prevent them from developing in the first place.

The above preventative measures can help you take good care of your bettas and protect them from potentially lethal cancerous tumours.

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