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14 Common Betta Fish Diseases: How To Identify And Treat Them

Betta fish are susceptible to various diseases; some are more prevalent than others. You can’t predict if or when your fish will get sick or what disease they might catch. However, if you can detect ailments in the early stages and provide timely treatment, you can prevent any fatal impacts.

The following is an all-encompassing guide to common betta fish diseases, shedding light on their causes, symptoms, and effective remedies. Moreover, below, you’ll find tips on preventing bettas from getting sick and how to safely medicate diseased fish.

How To Tell If Your Betta Fish Is Sick?

betta fish diseases
Virtually all fish health problems can be traced to stress. It is one of the main culprits responsible for sickness. Prolonged or chronic stress weakens the fish’s immune system, making them more vulnerable to bacterial, fungal, or parasitic infections.

The telltale signs of a stressed betta fish include loss in appetite, lethargic behavior, or change in appearance, such as developing stress strips, a paler body, or clamped fins.

These are the general signs of stress and are often harmless. However, if they last long, take it as an indication of disease onset.

Identifying and removing the stressor will help your fish return to its normal state. However, if left unattended, it can lead to severe illness or even death of your aquatic companion.

Diseased Betta Fish Signs & Behavior

  • Refusal of food
  • Lying at the bottom of the tank or hiding more than usual
  • Discoloration, ragged fins, or spots on the body
  • Erratic swimming patterns such as swimming sideways, floating uncontrollably, twitching, or struggling to maintain balance
  • Visible bacterial or fungus infections – signs include bloody patches on the body/fins, cloudy eyes, open sores, or excessive slime coat production.
  • Fish scratching or rubbing against objects is a sign of parasite infestations.
  • Stringy or discolored feces is a sign of constipation
  • Labored breathing or gasping at the surface

Common Betta Fish Diseases – Causes, Symptoms, and Remedies

Betta fish diseases can be categorized into bacterial, fungal, and parasitic infestations. Fungal infections are less common than parasites and bacteria.

Parasitic Disease In Betta Fish


betta fish diseases
Ich, or white spot disease, is caused by the protozoan parasite called Ichthyophthirius. It’s an external parasite that attaches to the fish’s fins, body, and gills, forming tiny white dots.

Newly added fish are particularly vulnerable to Ich infections due to the stress associated with transportation and acclimatization to a new environment. Ich is a highly contagious disease that spreads rapidly from one fish to another.

Signs and symptoms:

  • The most noticeable sign of Ich infection is tiny crystals on the body and fins, like someone has sprinkled salt on the fish.
  • Other symptoms may include loss of appetite, rapid breathing, fish rubbing their bodies on decor items or gravel, lethargy, and hiding behavior.

Causes and contributing factors:

  • Stress
  • Contagious companions
  • Poor water quality


  • Quarantine your betta fish.
  • Gradually increase the tank’s temperature up to 81-86 degrees Fahrenheit.
  • Warm water holds less dissolved oxygen, so consider adding an airstone.
  • Add aquarium salt to the aquarium or use strong medications such as Rid Ich Plus, Ich-X, or Mardel Copper Safe.
  • Perform daily water changes.

NOTE: Do not stop the treatment early, even if the Ich seems to be gone.

Hole in The Head

betta fish diseases

Also known as Head and Lateral Line Erosion or HLLE, it is a common disease in freshwater fish. It appears as visible holes or open pitted wounds formed around a fish’s head, face, or along the lateral line.

The hole-in-head disease is not contagious and can be cured if diagnosed early. But in later stages, it becomes deadly and may not be reversed.


  • Early signs include small sores or pin-holes on the fish’s head or above the eyes. If left untreated, these cavities can lead to increasingly larger lesions over time.
  • Other symptoms include white, stringy feces, subdued coloration, and betta losing appetite.


  • Poor living conditions like overstocking, inadequate filtration, lack of water changes, and improper nutrition are major contributing factors to hole-in-the-head disease.


  • Metronidazole (sold as Flagyl) is the primary medicinal treatment for HLLE. Medicated food is most effective, but if your betta has stopped eating, you can add metronidazole directly into the water.
  • Remove all activated carbons from the filtration system during treatment.
  • Maintain optimal water conditions followed by regular water changes.
  • Feed your fish a balanced, protein-rich diet.
  • Get rid of environmental stressors (if any).


betta fish diseases

Known by different names, gold dust disease, coral disease, or rust disease, it’s a common infestation caused by dinoflagellate parasites. Velvet is highly contagious and can lead to fatality if not prevented early.


  • Velvet-infected betta fish appears brownish-gold with a rust-like dusting on the body, fins, and/or gills. It causes the fish to lose its slime coat.
  • You may also find your betta rubbing against objects to itch their bodies to get parasites off.
  • Other signs include lethargy, clamped fins, and respiratory distress.


  • Velvet disease in bettas is caused by ongoing stressors, such as poor water quality and prolonged exposure to colder water temperatures.


  • Medicate your fish using Mardel’s CopperSafe. Copper-based anti-parasite medicines are usually effective against gold dust disease.
  • A week-long blackout (complete darkness) is particularly helpful in eradicating the parasite as it partly depends on photosynthesis.
  • Raise the temperature to 80 degrees Fahrenheit
  • Discontinue carbon filtration during treatment.

Camallanus Worms

betta fish diseases

Camallanus worms are internal parasitic nematodes that live in fish intestines and feed on their blood. These worms aren’t always lethal but can cause internal bleeding and secondary bacterial infections.

Camallanus infection is fairly contagious. And there is a chance that the worms might have released microscopic larvae into the tank by the time you have detected the issue.

Therefore, to be on the safe side, it’s best to treat the whole aquarium rather than moving out the infected betta to a hospital tank.


  • Early or mild infections can be hard to diagnose because often there are no noticeable symptoms.
  • On the other hand, severe Camallanus infections can lead to small thread-like reddish brown worms sticking out of the fish’s anus. Mature worms are a couple of millimeters long.
  • Other symptoms of Camallanus worms in betta fish include, abdominal bloating, wasting, and disinterest in food.


  • Infected fish foods, especially live feeds like crustaceans, can contaminate an entire tank.


  • Fritz Expel-P, a deworming medication, contains levamisole as an active ingredient and has proven to be effective in curing Camallanus infections in fish.
  • These medications paralyze the worms, pushing them out of the gut and into the aquarium. After 24 hours of medicating the tank, thoroughly clean the substrate to remove the worms.
  • Due to the Camallanus lifecycle, usually, three treatments are required to eliminate the parasite, each one week apart.

Bacterial Disease In Betta Fish

Internal or external bacterial infections are relatively common in bettas. Treatments can be tricky for certain diseases and should be done cautiously, as some antibiotics may disrupt the aquarium’s biological filter.

Fin Rot

betta fish diseases

If your betta’s fins or tail looked tattered or discolored, it’s likely due to fin rot. It’s a common bacterial disease that affects the fin tips and tail, causing them to deteriorate.

Although fin rot is an easily treatable infection, it can quickly progress and lead to body rot or other series complication if neglected.


Depending on the severity of the infection, the signs may vary:

  • Mild fin rot: slightly ragged fins, brownish fin edges
  • Moderate fin rot: large fin disintegration, receding fin tips, black or red tattered edges, fuzzy growth on the fins
  • Severe fin rot: Massive loss/chunks of fins missing, bloody fin bases, increased inflammation and redness, open sores on fins, body rot.


  • It’s usually caused by poor water quality.
  • Common stressors such as overcrowding, higher bio load, and overfeeding/underfeeding can also weaken the fish’s immune system, thus making them susceptible to the disease.
  • Fin rot can also develop as a symptom of a fungal infection or other illnesses.


  • Maintaining clean water and ideal parameters can treat mild and moderate fin rot. Daily water changes are effective.
  • For optimum results, add aquarium salt.
  • In severe cases, medicate your betta using Fritz’s Maracyn 2 or Seachem’s KanaPlex.

Columnaris (Cottonmouth)

betta fish diseases

Columnaris is a common bacterial disease caused by Flavobacterium columnare. The infection typically affects the gills, the skin, and fins, resulting in gill necrosis and skin ulcerations followed by epidermal loss and fin erosion.

The disease can also lead to secondary infections with fungi, resulting in fuzzy cottony or wool-like growths around the fish’s head or mouth. This is why Columnaris has also termed cotton wool disease and mouth fungus.

It’s a highly contagious infection and can be fatal. Therefore, it should be prevented before it’s too late.


  • Gross signs of Columnaris disease include frayed fins, depigmented lesions on the skin, and necrotic gill lesions.
  • Secondary fungi infections appear as cottony growth or grayish-white patches around the head or mouth.
  • Another distinctive symptom of Columnaris is the development of a raised lesion on the back, like a saddle on the fish’s body.


  • Stress conditions and poor water quality (high nitrite levels and organic load)


  • Columnaris can be cured using antibiotic bath treatment. Use Kanamycin and Nitrofurazone together. Kanamycin is found in Seachem Kanaplex, and Nitrofurazone is found in either Jungle Fungus Clear Fizz tabs or Furan-2.
  • You need at least 2 rounds of treatments.
  • It’s best to have the antibiotics in the tank for 7-10 days to mitigate the infection from your betta’s system.
  • Salt bath treatments can be used for disinfecting water contaminated by F. columnare.
  • For severe infections, you may require systemic antibiotic therapy.


betta fish diseases

Dropsy is not a disease but rather a physical manifestation or a sign of an underlying issue the fish might be suffering from. The fluid buildup causing abdominal swelling and protruding scales can be a symptom of kidney failure, liver dysfunction, or bacterial infection.

Curing dropsy is a complicated task and takes time. Treatment involves fixing the underlying condition and providing supportive care to the sick betta.


  • Extreme swelling in the abdominal area
  • Betta scales sticking out like a pinecone
  • Loss of appetite and hindered ability to swim
  • Fish stay closer to the surface for oxygen


  • Kidney failure in bettas (that lead to dropsy or excess water retention) can be caused by a virus, bacteria, or parasitic infection.
  • Poor nutrition, environmental or genetic factors can also be responsible for the condition.


  • While dropsy is not always treatable, antibiotics or Epsom salt in a hospital tank are known to produce positive results.
  • Recommended antibiotics for dropsy include SeaChem’s KanaPlex (or any other kanamycin-based medication) or Mardel Maracyn II.


betta fish diseases

If your betta’s eye has swelled up or bulged outward, he’s suffering from Popeye. This disease can affect one or both eyes, causing them to enlarge or protrude from the sockets.

Popeye can be cured, but if left untreated, it can result in the betta losing its eyesight permanently.


  • Bulging eye.
  • Protrusion of one or both eyeballs.
  • Cloudiness of the eyeball.
  • Expansion of the eye sockets
  • Eye rupture


  • Prolonged exposure to poor water quality.
  • A result of injury or bacterial infections.
  • Sometimes, Popeye can be a sign of Tuberculosis, a fatal fish disease.


  • First of all, test your water parameters. Ammonia and nitrite should be at 0 ppm, nitrate below 20 ppm, and pH at 7.0
  • If the test reading measures elevated toxins, carry out water changes.
  • Give your betta a salt bath treatment.
  • If Popeye results from an injury, your betta will heal on its own as long as the condition doesn’t lead to secondary infection.
  • Lastly, when nothing seems to work, take the help of antibiotics – Maracyn II or Kanaplex.


betta fish diseases

The bloody red streaks across the betta’s body are a telltale sign of Septicemia. It’s not a disease but rather a symptom of bacterial infection. Septicemia is rare and mainly affects stressed, wounded, and weakened fish. It may also develop as a secondary infection to Popeye.

Septicemia is not contagious, but if left untreated, it can lead to organ failure, resulting in the death of your aquatic companion.


Septicemia can be hard to diagnose on red-colored betta fish.

  • Dark red outlined blood vessels along the fin tips and under the scales
  • Red marks may also be noticed around the mouth
  • Lethargic behavior
  • Refusal of food
  • Unstable swimming pattern


  • Internal bacterial infection in the bloodstream
  • Adding new tankmates without quarantining can spread the disease
  • Poor water conditions
  • Feeding infected food, mainly live food
  • Chronic stress


  • Higher nitrite concentration can also cause redness or streaks under the scales. To rule out this possibility, perform a water test.
  • Keep your water pristine quality.
  • Unless the underlying issue is known, it’s difficult to suggest medication. However, you can go for Minocycline (Maracyn II). It’s used for treating a broad spectrum of bacteria and has some decent success rates for curing Septicemia.
  • Kanaplex is another highly recommended medication.


A rare (in the case of betta fish) but deadly disease, Furunculosis is highly contagious that affects fish of all ages. It’s caused by a common pathogen called Aeromonas salmonicida resulting in raised muscle lesions or skin boils.

Infected fish with open sores can readily spread the disease to other fish. Acute Furunculosis can cause death within a few days of initial clinical signs.


  • Hemorrhages on the skin, mouth, and fin bases
  • Chronic phases appear as large furuncle (boil) on the side of fish, progressing to crater lesions
  • Popeye
  • Respiratory distress
  • Loss of appetite
  • Darkening of body color and pale gills
  • Lethargic swimming or swimming just below the surface


  • Contact with infected fish or exposure to contaminated water
  • Poor water quality
  • Environmental stressors


  • Furunculosis in fish can be treated with sulfamerazine, sulfamethazine, and sulfaguanidine, as well as by chloramphenicol and terramycin.

Other Betta Fish Diseases

Fin Biting/Nipping

betta fish diseases

Fin biting and nipping are common behaviors noticed in betta fish. It involves fish biting at their own fins or the fins of their tank mates.


  • Constant biting or nipping can result in torn, frayed, or damaged fins, leaving the fish susceptible to infections.
  • In severe cases, rounded chunks can be missing from the fish’s fins, with no noticeable growth around the bites, unlike fish rot (which starts to heal itself as you maintain pristine quality water.)
  • Biting behavior eventually leads to fin rot.


  • Fin biting is typically a result of stress or boredom. It includes poor water conditions, inadequate diet, overcrowding, or lack of stimulation.
  • Male bettas are highly aggressive and may nip at each other’s fins during territorial disputes or as a form of dominance.


  • Maintain good water quality, provide proper nutrition, and ensure sufficient space.
  • Avoid overcrowding and choose compatible tank mates to minimize aggression.
  • Betta fins are delicate and can get caught on a lot of things. Make sure there are no sharp edges in your aquarium.

Bloat or Swimbladder Disorder

betta fish diseases

Fish bloating refers to a swollen or distended abdomen, often caused by overfeeding.

Swim bladder disorder, on the other hand, affects the swim bladder, impacting the fish’s ability to control its buoyancy. It can result in the fish having difficulty swimming or maintaining balance.


  • Swim bladder disorder can be caused by various factors, including infections, genetics, injury, or poor water quality.


  • If your betta’s bloat results from overfeeding, fast your fish.
  • Feed blanched, shelled-free peas if your fish is constipated (producing stringy feces).
  • Maintain optimal water quality.
  • In extreme swelling cases, slightly increase the water temperature and add Epsom salt to the tank.
  • If you suspect the cause of bloating is due to infection, medicate your betta with Maracyn II antibiotic.

Cloudy Eyes

betta fish diseases
Does your betta’s eye look hazy, milky, or cloudy? Fish eye cloudiness is not a disease but a symptom of an underlying sickness or an early sign of an upcoming illness.


  • Cloudy betta eyes can be caused by chemical imbalances, bacterial infection, internal parasites, nutritional deficiencies, or a physical eye injury.


Treating cloudiness involves addressing the underlying cause and taking preventive measures accordingly. However, if you feel clueless, do this:

  • Conduct a water test to ensure toxins aren’t running high
  • Perform daily water changes
  • Get rid of stressors (if any)
  • Give your betta an Epsom salt bath
  • If the problem persists or worsens, consult a veterinarian for an accurate diagnosis and tailored treatment plan.

Betta Tumors

betta fish diseases

Fishes can develop tumors, much like humans and other animals. Most tumors appear as bumps or lumps under the fish’s skin unless it’s on internal organs which aren’t visible.

The good news is cancerous tumors in betta fish are quite rare. It’s possible that the lumps on your fish’s body could be an ulcer or an abscess.


  • Lumps on the body or fins
  • Progressive tumors affect the fish’s ability to eat and swim, resulting in a rapid decline in overall health.
  • Internal tumors symptoms are hard to diagnose


  • The exact causes of fish tumors are not well understood, but genetic predisposition, unfavorable environment, and viral infections may contribute to the disease.


  • Unfortunately, most cancers found in fish have no cure or treatment.
  • Some tumors are treatable, such as gill tumor, which is caused by a thyroid problem and can be cured by Epsom salt or medicated baths.
  • Tumors on internal organs are not detected until the advanced stages when it is too late to save the fish.

Can Betta Fish Diseases Be Prevented?

An ounce of prevention is worth a pound of the cure.

Environmental stress is a major factor in the outbreak of fish diseases. It weakens their immune system, making them sick and prone to deadly infections.

Sources of fish stress include higher ammonia/nitrite levels, inadequate filtration, temperature fluctuations, improper diet, overcrowding, aggression, etc.

So, the first step towards keeping the diseases at bay is, getting rid of the stressors, making regular water changes, and providing your betta with optimum habitat, ideal water parameters, and a balanced nutritious diet.

Most importantly, always quarantine new fish before adding them to the main tank. New fish may carry infections or parasites without showing any symptoms initially. By isolating them in a separate tank for a few weeks, you can closely monitor their health and behavior.

If any signs of illness are displayed during this quarantine period, you can take appropriate measures to treat the fish without exposing the entire aquarium to potential harm.

Early Detection and Timely Prevention Is The Key

Being able to diagnose diseases at an early stage allows for prompt intervention and treatment, increasing the chances of successful recovery. Moreover, swift action can help prevent the disease from spreading to other fish in the tank.

Observing your betta fish daily enables you to detect any signs of abnormal behavior, changes in physical appearance, or appetite.

Things To Keep In Mind When Medicating Betta Fish

  • Use a quarantine tank: consider medicating your betta in a separate tank to avoid any adverse effects on other fish in the aquarium.
  • Accurate diagnosis: it’s crucial to correctly identify the disease or condition your fish is suffering from to select the appropriate medication.
  • Follow instructions: strictly adhere to the medication directions, such as dosage, frequency, and duration of treatment.
  • Remove carbon filtration: activated carbon should be temporarily removed from the filter as it absorbs the drugs from the water, resulting in reduced effectivity.
  • Monitor closely: during treatment, monitor your betta closely for any adverse reactions or changes in behavior. Adjust the treatment if necessary.
  • Complete the full course: never stop the treatment prematurely, even if your betta fish appears to have recovered. By adhering to complete treatment duration, you ensure total eradication of the disease, reducing the risk of a relapse.
  • Seek professional advice: If you’re unsure about the best course of action or if the condition worsens despite treatment, consult a veterinarian or experienced fish keeper for assistance.

Medicated Food Vs. Medicated Baths: What’s Better?

The treatment method should be determined based on the specific disease or condition you want to cure.

Medicated feeds are particularly effective for treating internal parasites. You can buy commercially available medicated food (formulated for the disease affecting your betta) or make it on your own by mixing the medicine with the fish’s regular diet.

If your bettas refuse to entertain treated food, soak it in garlic juice to make it more appealing.

Bath treatments involve immersing the fish in a medicated solution. This method effectively treats external parasites, bacterial infections, or certain fungal infections. It provides direct contact with the affected areas.

However, medicated baths can be stressful for fish, so careful monitoring is necessary.

In some instances, a combination of both methods may be recommended. This allows for full-scale treatment, targeting both internal and external issues.

Wrapping Up

As mentioned earlier, you cannot predict when your betta fish might get sick or which disease they may come into contact with. But, being familiar with common ailments and their symptoms enables you to detect the disease and quickly begin the treatment.

Regular monitoring and proactive care are essential for the well-being of your aquatic pet.

Lastly, please note that this article is intended for educational purposes only and should not substitute professional veterinary advice.