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Common Betta Fish Diseases: Prevention, Signs, & Treatment

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By Lindsey Stanton

A poorly looking red betta fish in an empty hospital tank

When it comes to aquarium fish, the beloved betta may be without equal for pure elegance. Vivid colors, flowing fins, and graceful movements are the hallmarks of the betta fish and the reasons why their owners love them.

As a doting betta owner, you’ll want to keep your fish as healthy and happy as possible. And though they are generally kept as solitary specimens, betta are susceptible to a variety of diseases, just like any other fish. This guide to betta fish diseases will help you learn to identify and deal with the many illnesses and disease your fish might face, and how to maintain a healthy environment for your fish.

In this article we take a look at a few common betta diseases and symptoms, as an exercise in education, so you can spot when your betta may be feeling unwell, and take steps toward finding them treatment. We describe the causes, symptoms, and treatment of many of the most common diseases that affect betta, so this is important reading not just for curing illness, but for preventing it in the first place and keeping healthy betta. 


An Ounce of Prevention

Fashionclubs Betta Bead Leaf Hammock
Image Credit: Fashionclubs, Amazon

What’s better than getting over an illness? Not getting sick in the first place! If you take good care of your betta’s home, you will greatly reduce the opportunity for disease to strike.

Room to Move

Many betta owners mistakenly believe they can keep their fish in a tiny container, especially since it was probably purchased in a plastic cup. But, like any fish, a betta likes some space to exercise and explore. So while it can live in a small cup or bowl, it won’t thrive.

Still water turns stagnant quickly, and that leads to sick fish. Choose a proper aquarium setup with heat, lights, and filtration. It’s better for the fish, and frankly, it’s more fun for you!

Keep It Clean

Now that you’ve chosen an appropriate home for your pet, it’s up to you to keep it neat and tidy. While betta can be trained to a certain degree, I haven’t seen one yet that cleans its own tank! Without getting into a detailed how-to guide for betta care, here are some key points for maintaining a healthy tank:

  • Regular water changes
  • Keep water temperature between 75°–82°
  • Feed an appropriate and varied diet
  • Quarantine any new fish (or other tank-mates), or plants before introducing them to the tank
  • Do not overfeed
  • Remove uneaten food immediately
  • Wash your hands before and after contact with the tank

These are all simple things you can do to help reduce the risk of disease from unsanitary conditions or cross-contamination. Other than the temperature range (which will vary by species), you can apply these steps to the care of any aquarium.

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Timing Is Everything

dumbo halfmoon betta
Image Credit: panpilai paipa, Shutterstock

Treating an illness in its early stages is the surest way to have a successful outcome. Some betta diseases can prove fatal within a day or so, which leaves precious little time for a pet store run, and no time at all for a special order.

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Keep a First Aid Kit – Hope For the Best, Prepare For the Worst

A red case style first aid kit isolated on white

It might sound funny, but keeping a first aid kit ready and handy is an excellent idea for any fish owner, and should in our opinion be classed as an essential kit for routine betta fish care.

If you or someone in your family is sick or injured, you probably have what you need to treat the problem stored in a medicine cabinet or kit somewhere, right? So why would you wait for your fish to be sick before going out to find the right medicine?

What To Put In Your Betta First Aid Kit

Bettafix – A natural antibacterial (contains Tea Tree extract) that can be used for fungus, wounds, ulcers, and rot. Promotes regrowth of scales and fins.

Ampicillin – Antibiotic used for pop-eye, Gram-positive infections (in fish these are typically Mycobacterium and Streptococcus), and Gram-negative infections (such as Pseudomonas, Aeromonas, and Vibrio).

Kanamycin – Antibiotic for major bacterial infections. Has also been shown to be highly effective in treating severe fin rot.

Jungle Fungus Eliminator – Anti-fungal treatment in a fizz-tab form. Good for fungus, tail, fin, or mouth rot, hemorrhagic septicemia, clamped fins, dropsy, eye cloud, pop eye, and swim bladder disease. Works quickly, but be sure to dose appropriately; a full tab is for a 40-gallon tank!

Tetracyclin – An easily found antibiotic for less severe infections.

Maracin 1 and Maracin 2 – Anti-fungal and antibiotic medications good for mild infections such as fin rot.

A Note On ‘Preventative Medicines’

You might think you’re doing your fish a favor by using aquarium water additives to prevent any diseases before they start. Indeed, many experienced fish keepers recommend them and all aquarium and pet stores sell such products, typically antibacterial and antifungal fluids.

However, your aquarium water is full of bacteria at all times, and most of it is beneficial. Even potentially harmful bacteria will typically not hurt your fish if their immune system is strong. By using antibacterial medicine when no signs of infection are present, you may end up hurting the good bacteria, (leading to an unbalanced ecosystem) and you provide the bad bacteria with a chance to adapt to the medicine.

Should that happen, the antibacterial medicine might not help at all if your betta becomes sick. Your best bet is to practice good aquarium maintenance; that’s all the disease prevention they really need!

Other Items To Keep Handy

Silver and orange betta fish
Image Credit: ivabalk, Pixabay

Be armed and ready with these betta must-haves!

  • 1-gallon containers – perfect hospital tank for treatment before transferring to a quarantine tank.
  • Aquarium Salt – good for stressed fish and eliminating external parasites, but should not be used with live plants.
  • Epsom Salt – can be used in a hospital tank to treat constipation and dropsy.
  • Quarantine tank – for housing fish after treatment. Here they can be observed closely to be sure they are healthy before returning to the main tank.


Check Water Chemistry Before Treating


It’s possible that poor water quality is the reason your betta seems unwell. Check your water with liquid test kits and perform a water change if the results indicate unsafe water. Common toxic substances that build up in an aquarium to create poor water conditions are ammonia, nitrite, and nitrate, all of which can make for sick betta fish.

Let’s look at the symptoms of poisoning by each of these potential culprits.


Ammonia is a part of your betta’s biological waste, and it will build up if the water is unfiltered. Because even mild concentrations of ammonia can burn a fish’s gills, If you see your betta darting about frantically and gasping for air at the surface, you may be looking at ammonia poisoning.


Nitrite – the excretion of friendly and needed ammonia-eating bacteria, nitrite is a naturally occurring part of your aquarium’s ongoing cycle. However, too much nitrite (and it doesn’t take much!) can impair blood circulation, and cause the gills to turn brown (known as “Brown Blood Disease”). Look also for rapid gill movement and lethargy.


Nitrate – a chemical excreted by the bacteria that feed on nitrite. (There’s a lot of excreting in an aquarium!) Very high concentrations can cause the spine to bend and the body to curl. Watch for erratic swimming and twitching.

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The 3 Types of Betta Fish Diseases

betta fish fin loss
Image Credit: Wirestock Creators, Shutterstock

There are many different common betta fish diseases that betta might succumb to, but they can be broken down into three categories: parasitic, bacterial, and fungal.

1. Parasitic

Parasites are unwanted guests in any tank! They generally arrive via contaminated fish or water introduced to the tank. Treatments include antibiotics, water changes, and the addition of salt.

2. Bacterial

Bacteria are with your fish all the time but don’t become a problem until an opportunity arises, such as a wound, injury, or an immune system weakened by stress or some other malady. Antibiotics are the most common treatment.

3. Fungal

Like bacteria, fungal infections sometimes occur when another problem exists, such as an injury. These growths can be very harmful, even fatal to your fish. Antibiotics and antifungal medicines are typically used for treatment.

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Signs of a Sick Betta Fish

A closeup shot of sick betta fish in aquarium tank
Image Credit: Wirestock Creators, Shutterstock

You know your betta better than anyone. If you see any behavior that’s out of the ordinary, or if part of their body and fins looks unusual to you, trust your instincts and immediately assess what disease you may be dealing with. Remember, treatment in the early stages of any condition is most likely to have a good outcome and any delay could even lead to death.

Here are some telltale signs to be watching for that may indicate the presence of one or more betta fish diseases:

  • Swimming into objects and rubbing against them
  • Fading color
  • Swollen eye(s)
  • Swollen or hollow belly
  • Inflamed and/or reddened gills
  • Raised scales
  • Clamped fins (held close to the body)
  • Open sores
  • Inactive
  • Not eating
  • Lumps, spots, or cottony growths
  • Stays at the bottom of the tank or,
  • Stays in a corner at the surface

If you observe any of these signs, you have a sick fish on your hands!

Isolate Sick Fish Immediately

Betta fish alone in a hospital tank
‘Salamander betta 2’ by hiwarz on Flickr (CC BY 2.0)

If your betta shares its tank with any other fish or aquatic creatures, move it to a quarantine or hospital tank immediately upon identifying it as sick, regardless of the nature of the disease.

The last thing you want is to expose your other tank residents and risk an aquatic epidemic. You also don’t want to medicate healthy fish unnecessarily. So transfer your betta to a hospital tank (a separate tank you can medicate just the sick fish in) and allow it to heal and convalesce in isolation.


The 17 Most Common Betta Fish Diseases:

As I alluded to before, there are numerous diseases your betta might contract during its lifetime. Here is a list of common ailments, how to identify them, and brief details on what you can do about them.

1. Ammonia Poisoning

Betta with skin disease
Image Credit: Lienda Yunita Apponno, Shutterstock

Description: Ammonia (NH3) is a weak base that causes burns to the gills.

Common or rare: Common in unfiltered tanks.

What causes ammonia poisoning: A build-up of ammonia, which is found in fish waste.

Symptoms of ammonia poisoning: Gasping for air at the surface is the main symptom, accompanied by darting motions.

Treatment of ammonia poisoning: Change aquarium water. Reduce or eliminate feeding for a couple of days to reduce ammonia output.

2. Bacterial Infection/Open Red Sores

Description: There are many different kinds of bacterial infections. Can be highly contagious. The potential for fatality varies, but should always be taken seriously and treated immediately.

Common or rare: Common

What causes bacterial infection/open red sores i: Bacteria are always present in your aquarium. Infections occur when the immune system is compromised by injury, stress, or other diseases.

Symptoms of bacterial infection/open red sores: Red sores or red patches, loss of appetite, color loss, clamped fins, sitting at bottom or top of the tank, not moving

Treatment of Bacterial infection/open red sores: 75%-100% water change and thorough cleaning. Isolate sick fish from the community. Add a small quantity of Aquarium Salt. Treat with Sulfa, Tetracycline, or Erythromycin.

3. Constipation

sick betta in aquarium
Image Credit: Wirestock Creators, Shutterstock

Description: Difficulty excreting waste due to a digestive blockage. Non-contagious, but potentially fatal if untreated, and a very commonly seen issue!

Common or rare: Common

What causes constipation in betta: Generally dietary in nature; possible causes include overfeeding, a lack of fiber, or food that’s too dry.

Symptoms of constipation: Bloating of the belly, lack of defecation.

Treatment of constipation: Withhold food for 1–2 days to allow the blockage to pass naturally. Feeding the inside of a pea can help constipation, as can gradually increasing the temperature of the water (if you generally keep your aquarium on the cool side) to around 80°F.

4. Costia

Description: Contagious parasitic infection introduced by infected fish added to the tank.

Common or rare: Rare

What causes costia: The protozoa Ichthyobodo necatrix, a.k.a. Costia necatrix.

Symptoms of costia: Cloudy, milky skin, protruding flagella (appendages) from the parasite. Fish may attempt to scratch and show a loss of appetite.

Treatment of costia: Isolate fish in a quarantine tank. Administer Aquarium Salt baths or Trypaflavine. Raise the temperature of the aquarium to 90°F for 3 days (while betta is in quarantine) to kill parasites left behind.

5. Dropsy

Description: Internal bacterial infection causing renal system failure. Typically fatal, but not contagious if the affected fish is still alive.

Common or rare: Common

What causes dropsy: Generally brought on by poor living conditions and/or malnutrition.

Symptoms of dropsy: Raised scales, bloated belly, pinecone-like appearance.

Treatment of dropsy: Metronidazole, Tetracycline, or edible Anti-fungal pellets.

6. External Parasites

Description: Parasitic creatures living on the outside of the betta (such as anchor worms). Can be fatal, but readily cured.

Common or Rare: This can be common in community tanks, but easily avoided by quarantining new specimens.

What causes external parasites: Almost always introduced by new fish or other aquarium creatures.

Symptoms of external parasites: Darting motions, and scratching. Parasites are usually visible under magnification.

Treatment of External parasites: Do a complete water change and use Aquarium Salt for minor cases. Try an anti-parasitic medication, such as Tetra Parasite Guard, if salt is not effective.

7. Betta Fish Fin Rot or Tail Rot

Betta with fish fin rot
Image Credit: SoReaux, Shutterstock

Description: Bacterial infection causing degradation of the tail and/or fins. Non-fatal except in extremely advanced cases. If caught early, fins and tail should grow back.

Common or Rare: Common

What causes fin rot/tail rot: Dirty water can lead to this bacterial infection, as can suffering damage to the fins or tail. Damage can be caused during handling, or by catching on sharp ornaments.

Symptoms of fin and tail rot: Edges of their fins and tail will look torn or frayed, and pieces may be missing. Affected edges may be lined with either black or white.

Treatment of fin rot/tail rot: Aquarium salt may help, or any ant-bacterial medication.

8. Fungal Infection

Description: Fungus growing on the exterior of the fish. Generally a slowly progressing infection, but fatal if not treated in the early stages. Highly contagious.

Common or rare: Common

What causes fungal infection: Fungus is opportunistic and will usually appear after another infection, or after an injury.

Symptoms of fungal infection: White patches that look like cotton are the main symptom. Lethargy, muted color, loss of appetite, and clamped fins are all possible symptoms.

Treatment of fungal infection: Isolate sick fish if part of a community. Water changes every few days and anti-fungal medication.

9. Ich, Ick, or ‘White Spot Disease’

Betta with white spot disease
Image Credit By: pang147, Shutterstock

Description: Ichthyophthirius multifiliis, a highly contagious parasitic infection. Usually fatal, but generally responds well to treatment when caught early.

Common or Rare: Common

What causes ich (ick, white spot): A protozoan called Icthyophthirius capitalizes on a weakened immune system, typically in a stressed fish. Stress is often caused by a change in water condition or another infection.

Symptoms of ich: Small white flecks on the body resembling grains of salt. Loss of appetite, hiding, resting on the bottom, and scratching, are other signs.

Treatment of ich: Raise the temperature of water to 80°F–85°F, and treat with anti-parasite or Ich-specific medication.

10. Inflamed Gills

Description: A swelling of the gills, which may partially or completely prevent them from closing. Prevents the fish from breathing properly and is fatal.

Common or rare: Common

What causes inflamed gills: There is more than one possible cause, including bacterial infections and ammonia/nitrite/nitrate poisoning.

Symptoms of inflamed gills: One or both gills will appear swollen and red, and will not close properly. betta will likely be gasping for air.

Treatment of inflamed gills: Isolate the affected fish, and perform a full water change every 3 days. Test your water (or have it tested) to see if water quality is the culprit. Treat with antibiotics for infections, or for poisoning, water changes alone should be enough to clear the problem, though the addition of a stress coat and/or aquarium salt may also help.

11. Internal Parasites (intestinal)

Description: Protozoa living inside the fish, such as Nematodes (roundworms). Cannot be observed directly. Typically fatal, eventually, if untreated. Not contagious, but an entire aquarium system can be infested.

Common or rare: Common

What causes internal parasites (intestinal) in betta: Parasites are introduced by new fish (or the water they came in) that are carrying the parasite or eggs.

Symptoms of internal parasites: Though you cannot see the parasite, you will notice the betta losing weight, despite a healthy appetite, due to the parasite stealing the nutrients.

Treatment of internal parasites: Do 100% water changes (75% in large tanks) daily, and thoroughly clean gravel or other substrates to remove any eggs or larvae. Treat with anti-parasite fizz tabs or pellets.

12. Popeye

Description: Exophtalmia, swelling of the eye, or eyes. Possibly contagious, depending on the cause. Unlikely to be fatal, though the loss of an eye is possible.

Common or Rare: Common

What causes popeye in betta: There are many possible causes including infection, rough handling or injury, gas embolism, tumors, or Vitamin A deficiency.

Symptoms of popeye: One or both eyes will swell and bulge, sometimes dramatically. The eye may actually pop out of the socket in extreme cases.

Treatment of popeye: Popeye can be difficult to treat, as the cause is not always evident. Water changes, antibiotics, and/or Bettafix are the best places to start.

13. Septicemia

Description: Also known as Sepsis, it’s an infection in the blood. Can be fatal in a short period of time. The condition itself is not contagious, but the bacteria causing it might be.

Common or rare: Common

What causes septicemia in betta: Infection of an open wound, or through ingestion.

Symptoms of septicemia: Red spots or streaks under the scales. Ulcers or open wounds, loss of color, loss of appetite, lethargy, and clamped fins are all possible symptoms.

Treatment of septicemia: Treat immediately with antibiotics for both gram-positive and gram-negative bacteria. Something with Metronidazole is an excellent choice.

14. Slime Disease

Description: An infection of one of the following parasites: Chilodonella uncinata, Icthyobodo, or Trichodinia. Contagious, with a high rate of mortality.

Common or rare: Rare

What causes slime disease in betta: These parasites are frequently found in aquarium water, but do not pose a threat unless the fish is stressed or the immune system is weakened for some reason.

Symptoms of slime disease: Betta will produce excess slime (mucus) that will appear to be sloughing off the fish in the early stages. Later stages will bring scratching, loss of appetite, and heavy breathing.

Treatment of slime disease: Use medications with formalin or copper sulfate for best results. Increasing the temperature of the water and adding salt have also proven effective.

Sick Malay fighting betta
Image Credit By: Ismail Sadiron Pictures, Shutterstock

15. Swim Bladder Disease / Swim Bladder Disorder (SBD or Bloat)

Description: Swim bladder disease is a condition affecting the Swim Bladder, though not actually a disease. Non-contagious, and rarely fatal.

Common or rare: Common

What causes swim bladder disease (SBD or bloat) in betta: Can be caused by damage to the swim bladder through injury, or by pressure from constipation.

Symptoms of SBD: Extreme difficulty swimming, especially through the vertical plane. Betta may either float or sink and will have trouble compensating. If caused by constipation, bloating will be apparent.

Treatment of SBD: If bloat is present, treat constipation with the inside of a pea and/or fasting. If an injury is suspected, it should heal over time.

16. Tuberculosis

Description: A bacterial infection that is highly contagious and virtually always lethal to fish. Can be spread to humans.

Common or rare: Rare

What causes tuberculosis in betta: A bacterium known as Mycobacterium marinum. It is a close relative of Mycobacterium tuberculosis, which causes TB in humans.

Symptoms of tuberculosis: Lesions, loss of scales, extreme weight loss, and deformation of the skeleton.

Treatment of tuberculosis: You might try treatment with medications such as Kanamycin, but there is little chance for success. Euthanizing your betta (and its tank mates) may be the only option. Empty the tank and clean thoroughly with bleach, using extreme caution. Dispose of all ornaments and tools to prevent a new outbreak.

17. Velvet, or ‘Gold Dust Disease’

Description: A parasitic infection that begins on the exterior of the fish, and then works its way into the skin, blood, and gills. Contagious, and can affect all fish in a tank, as part of the lifecycle of the parasite is spent in the water searching for a host.

Common or rare: Common

What causes velvet, or ‘gold dust disease’ in betta: A parasite known as Piscinoodinium adheres to the betta and eventually penetrates the skin. Anything that encourages the parasite (cool water, too much light), or suppresses the immune system (stress, poor water, etc.) can allow Velvet to take hold.

Symptoms of velvet disease: Affected fish will appear to be sprinkled with gold dust in the latter stages. Heavy breathing, clamped fins, and scratching are other symptoms you may observe.

Treatment of velvet disease: Isolate the sick fish. Perform a 100% water change and clean substrate. Dimming or removing light may help as it prevents the parasite from photosynthesizing. Raising the water temperature to around 85°F will also hinder the life cycle of the bacteria. Use anti-parasite medications or something with Copper Sulfate.


As is the case with all pets, feeding your bettas properly and maintaining a clean environment will prevent most diseases from ever being an issue and maintain a healthy betta.

My experience as an aquarist has shown me, however, that no matter how hard you try, eventually, you’ll have a sick fish to deal with.

By being prepared with the first aid kit outlined above, and having your hospital tank ready to go, you’ll be ahead of the game. It cannot be stressed enough how important it is to start treatment early! Observe your betta regularly, and get to know its habits and appearance. Do this, and you’ll recognize the first signs of trouble immediately. With proper treatment, your betta will, hopefully, be back to its graceful, majestic, King-of-the-Tank self soon.

We hope the combination of your diligence, combined with the help of our guide above, will keep most if not all betta fish diseases at bay, but that if they do strike, that you can recognize them early and get your fish back to good health.

Featured Image Credit: Yasin Fadlilah, Shutterstock

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