Betta Fish Tuberculosis: Symptoms, Treatment, Prevention

betta fish tuberculosis
Table of Contents

Tuberculosis (TB) is one of the severe diseases that betta fish can encounter during their life.

Aquarists, especially betta owners, are deeply concerned about this disease because of its high mortality rate.

It’s also difficult to cure unless you catch it in the early stage and apply an effective treatment to it.

The consistent mutation of Mycobacterium (the bacterium responsible for tuberculosis) has further exacerbated the situation.

Each new variant of this bacterium is responsible for a different strain of TB in betta fish, making it extremely difficult to cure.

In this situation, you must know what to do if your betta catches TB.

In this article, you will learn about the causes, symptoms, treatment, and tuberculosis prevention in betta fish.

Exactly what is betta fish tuberculosis?

Like humans, animals, especially freshwater fish species, are susceptible to tuberculosis.

It’s a bacterial infection caused by a bacterium called Mycobacterium marinum. This bacterium is found in abundance in freshwater aquariums.

It’s believed to grow, populate, and thrive in freshwater, making it difficult to eliminate.

There’s also a theory about Mycobacterium marinum residing on the fish’s skin, but it has no supportive evidence.

One of the most dangerous aspects of tuberculosis is that it shows symptoms much later than its attack.

You may not notice any symptoms for even six months after the infection. That’s why tuberculosis falls in the category of the deadliest disease in betta fish.

The primary target of Mycobacterium marinum is betta’s internal organs (liver and kidneys in most cases).

The bacterium continues to damage the organs without showing any symptoms.

Once the organs begin to fail due to infection, the symptoms start to show up.

By then, the chances of your betta’s survival are slim.

What causes tuberculosis in betta fish?

As mentioned earlier, Mycobacterium marinum is responsible for tuberculosis in betta fish.

So, any factor that contributes to this bacterium’s growth, population, and activity can show up as the cause of TB.

In this context, the following factors can be considered as the causes of tuberculosis in bettas:

  • Poor water quality

One of the common factors that can cause your betta fish to contract tuberculosis is poor water quality.

Mycobacterium marinum thrives in poorly maintained water conditions where ammonia, nitrites, and nitrate levels are high, with excessive buildup of food leftovers.

Poor water quality can also result from overcrowding your aquarium because when you keep more fish in a small place, the bioload will be higher, polluting the aquarium water.

  • Sudden changes in temperature and pH of the aquarium water

Betta fish are sensitive to even a minor change in water parameters.

So, when the temperature or pH of the aquarium water rises or falls suddenly, it may leave your betta fish shocked or stressed, which may negatively impact the capacity and capability of their immune system to fight off tuberculosis.

Thus, fluctuations in temperature and pH of water can make your betta fish susceptible to TB.

Experts believe that Mycobacterium marinum breed and grow more efficiently in a warm environment.

So, when the aquarium water temperature rises too much, it becomes a perfect place for the tuberculosis bacteria to bloom.

In any case, sudden fluctuation in water parameters is not favourable for your betta’s health.

  • Lower-quality diet

If you’re not providing enough nutrients for your betta to grow and stay healthy, its immune system might weaken, causing it to fall sick and contract tuberculosis.

This isn’t just exclusive to tuberculosis, but all diseases that bettas are susceptible to. That’s why it’s essential to feed your betta fish a balanced diet.

  • Stress

As mentioned earlier, stress contributes to the weakening of the immune system of betta fish, making them susceptible to tuberculosis.

Besides fluctuations in temperature and pH of the water, many other factors can trigger stress in bettas, such as a violent tankmate, lack of decorations and live plants in the aquarium, poor diet, or any sudden changes in the living environment.

If you notice that any of these factors are causing your betta fish to become stressed out, you should react immediately to correct the situation.

Remember that your betta must have a strong immune system to deal with tuberculosis.

  • Introduction of affected fish in the aquarium

New fish serve as a significant carrier for tuberculosis bacteria.

They can spread the disease to healthy fish after getting into their aquarium. So, adding an infected fish to your betta’s aquarium can put them at risk of contracting tuberculosis.

You should keep the new fish in quarantine for at least 15 days to ensure you’re not harbouring any bacteria, viruses, or diseases.

That will help you keep your healthy betta safe from TB.

Symptoms of tuberculosis in Betta fish

Spotting the symptoms of tuberculosis can help you stop its spread to healthy fish.

Due to the late appearance of the symptoms, it is usually difficult to diagnose TB in your betta fish.

TB causes severe damage to betta’s internal organs, especially kidneys, liver, and intestine, before showing off its symptoms.

Here are some common symptoms you may notice in your betta fish infected by TB:

  • Anorexia (loss of appetite) and emaciation

One of the most noticeable symptoms of tuberculosis in your betta is loss of appetite.

After getting infected by Mycobacterium marinum, they may stop eating temporarily or permanently in severe cases.

Due to loss of appetite, your betta fish may experience nutritional deficiencies that can appear in the form of emaciation.

Bettas suffering from TB tend to lose their body weight faster. They can develop thinness if the loss of appetite is prolonged.

At the severe stage of tuberculosis, your bettas could begin to lose their muscle density which could lead to posture problems – usually causing scoliosis.

However, they’re not a clear indication of TB, as loss of appetite or emaciation can also be caused by many other diseases.

  • Scoliosis (Curved Spine)

As mentioned earlier, tuberculosis attacks the internal organs of betta’s body.

When the organs, like kidneys or liver, are attacked by TB, they begin to swell up and push against the spine, causing it to become vertically curved.

If you notice that the spine of your betta fish is curved vertically, it is the most apparent symptom of TB.

However, if the spine is curved horizontally, it can be due to dropsy.

In some cases, Mycobacterium marinum starts infecting the tissues and bones of the spine, bending its shape in the vertical direction.

So, tuberculosis can cause curved spine disease by damaging internal organs or directly attacking the spine.

  • Skin Issues

Betta fish suffering from tuberculosis may develop various skin issues, such as loss of scales and discolouration.

In severe infections, you may notice blood spots and open wounds on your betta’s skin.

Skin lesions in different body areas and folded fins are other symptoms you can expect to notice if your betta fish are infected by tuberculosis.

However, these skin defects are not limited to TB, as many other diseases can cause them.

  • Immobility or sluggish movement

Inactivity or loss of movement in your betta fish is another clear symptom of tuberculosis.

Your betta begins to lose movement at the start of the TB infection.

When the infection becomes critical, they may show complete immobility or inactivity.

The lack of movement is also associated with loss of appetite when they stop eating as they don’t have the energy to do so.

  • Eye damage

Besides the symptoms mentioned above, you may also notice eye damage in your betta fish.

It happens when the organs and tissues behind the eye begin to swell up after getting infected by tuberculosis.

They push the eye towards the outside, due to which you notice that it is protruding out of the eye socket.

The infected eye may also lose its colouration.

This type of eye damage is not a clear sign of tuberculosis, as it can also be caused by popeye or when your betta develops cloudy eyes.

Treating tuberculosis in betta fish

Although tuberculosis is a difficult-to-cure sickness, you can boost the chances of your betta’s survival by applying effective treatment.

You can also consult with your veterinarian to design a proper treatment plan for your betta fish.

Although various treatment options are available for tuberculosis, medication or drug therapy is the best treatment plan with a higher success rate.

In this treatment, you will medicate your betta fish with an antibiotic recommended by your veterinarian or local fish store.

You can follow these instructions to medicate your bettas:

  • Take a clean container that can accommodate 19 to 38 litres (5-10 gallons) of water. Fill this container with aquarium water. This is your quarantine tank in which you will medicate your betta fish. You can also place a gentle filter in the quarantine tank to eliminate any waste the fish produces.
  • Dissolve the recommended amount of medication in the quarantine tank.
  • Now, transfer your betta fish from the aquarium to the quarantine tank and follow the manufacturer’s instructions.

There’s a wide range of antibiotic medications available in the market that you can use to treat tuberculosis, such as Seachem Kanaplex, API Melafix, and Seachem Focus.

How to prevent tuberculosis in betta fish?

Fortunately, tuberculosis is one of the rarest diseases in betta fish. However, the possibility of your betta catching TB is always present.

If you want to prevent your betta fish from getting infected by tuberculosis in the first place, here are some useful preventative measures you can take:

  • Prevent your betta fish from becoming stressed out: Stress causes your betta’s immune system to become weakened. A weak immune system is highly susceptible to tuberculosis. Therefore, you should eliminate all factors triggering stress in your betta.
  • Maintain high water quality: If you maintain high water quality in the aquarium, the chances of Mycobacterium marinum’s survival and growth are slim. You should also perform regular water changes to keep the aquarium water clean.
  • Avoid overcrowding: Overcrowding leads to poor water conditions, which provides a suitable environment for tuberculosis bacteria to thrive. As the number of fish in your aquarium decreases, the water conditions will improve.
  • Quarantine new fish: Quarantine new fish for at least 15 days to ensure they’re not suffering from tuberculosis. This is the best prevention for tuberculosis.


Although TB is a life-threatening condition, you can prevent it from happening in the first place by taking the above-mentioned preventative measures.

The most common symptoms of tuberculosis include anorexia, scoliosis, skin issues, eye damage, and lack of movement.

If you notice these symptoms in your betta fish, you should immediately start the treatment with the correct antibiotic medication to boost the chances of your betta’s survival.

Leave a Reply

Your email address will not be published. Required fields are marked *

Posts you might like