Betta Fish Diseases, Symptoms and Treatment Guide

Betta fish diseases, symtoms and treatment guide written beside a sick looking betta

Photo Credit: © / foto76

When it comes to aquarium fish, the beloved Betta may be without equal for pure elegance. Vivid colors, flowing fins, and graceful movements; these 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 fish are susceptible to a variety of diseases, just like any other fish.

This guide will help you learn to identify and deal with the many illnesses and betta fish diseases you might face, and how to maintain a healthy environment for your fish.

An Ounce of Prevention

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 set up 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 Fish 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.

Timing Is Everything

Treating an illness in its early stages is the surest way to have a successful outcome.

Some betta fish 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.

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

A red case style first aid kit isolated on white

Photo Credit: © / scanrail

It might sound funny, but keeping a First Aid kit ready and handy is an excellent idea for any fish owner.

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

Be armed and ready with these Betta Fish 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

API FRESHWATER MASTER TEST KIT 800-Test Freshwater Aquarium Water Master Test Kit

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. (Please click here for our top recommendations for freshwater test kits.)

Common toxic substances that build up in an aquarium are ammonia, nitrite, and nitrate, all of which can make your fish sick.

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


Ammonia – 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 aquariums 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.

Types of Fish Disease

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


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 salt addition.


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.


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.

Signs of a Sick Betta

You know your Betta better than anyone. If you see any behavior that’s out of the ordinary, or if part of their body or fins look 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 watch for:

  • 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.

Identifying, Diagnosing and Treating 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.

Ammonia Poisoning

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

Common or Rare: Common in unfiltered tanks.

What Causes Ammonia Poisoning in Betta fish: A build up of ammonia, which is found in fish waste.

Symptoms of Ammonia Poisoning in Betta fish: Gasping for air at the surface, darting motions.

Betta fish Ammonia Poisoning Treatment: Change aquarium water. Reduce or eliminate feeding for a couple of days to reduce ammonia output.

Bacterial Infection/Open Red Sores

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

Common or Rare: Common

What Causes Bacterial infection/open red sores in Betta fish: 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 in Betta fish: Red sores or red patches, loss of appetite, color loss, clamped fins, sitting at bottom or top of tank, not moving

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


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

Symptoms of Constipation in Betta fish: Bloating of the belly, lack of defecation.

Betta fish Constipation Treatment: 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.


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

Common or Rare: Rare

What Causes Costia in Betta fish: The protozoa Ichthyobodo necatrix, a.k.a. Costia necatrix.

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

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


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 in Betta fish: Generally brought on by poor living conditions and/or malnutrition.

Symptoms of Dropsy in Betta fish: Raised scales, bloated belly, pinecone-like appearance.

Betta fish Dropsy Treatment: Metronidazole, Tetracycline, or edible Anti-fungal pellets.

External Parasites

Description: Parasitic creatures living on the outside of the Betta. Can be fatal, but readily cured.

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

What Causes External Parasites in Betta fish: Almost always introduced by new fish or other aquarium creatures.

Symptoms of External Parasites in Betta fish: Darting motions, and scratching. Parasites are usually visible under magnification.

Betta fish External Parasites Treatment: 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.

Fin Rot or Tail Rot

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

Common or Rare: Common

What Causes Fin Rot/Tail Rot in Betta fish: 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 Rot/Tail Rot in Betta fish: Edge will look torn or frayed, and pieces may be missing. Affected edges may be lined with either black or white.

Betta fish Fin Rot/Tail Rot Treatment: Aquarium salt may help, or any ant-bacterial medication.

Fungal Infection

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

Common or Rare: Common

What Causes Fungal Infection in Betta fish: Fungus is opportunistic and will usually appear after another infection, or after an injury.

Symptoms of Fungal Infection in Betta fish: White patches that look like cotton. Lethargy, muted color, loss of appetite and clamped fins are all possible symptoms.

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

Ich, Ick, or ‘White Spot Disease’

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

Common or Rare: Common

What Causes Ich (Ick, White Spot) in Betta fish: 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 (Ick, White Spot) in Betta fish: Small white flecks on the body resembling grains of salt. Loss of appetite, hiding, resting on the bottom, and scratching, are other signs.

Betta fish Ich (Ick, White Spot) Treatment: Raise temperature of water to 80°F - 85°F, and treat with anti-parasite or Ick-specific medication.

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 in Betta fish: There is more than one possible cause, including bacterial infections and ammonia/nitrite/nitrate poisoning.

Symptoms of Inflamed Gills in Betta fish: One or both gills will appear swollen and red, and will not close properly. Betta will likely be gasping for air.

Betta fish Inflamed Gills Treatment: 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 stress coat and/or aquarium salt may also help.

Internal Parasites (intestinal)

Description: Protozoa living inside the fish, such as Nematodes (round worms). 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 fish: Parasites are introduced by new fish (or the water they came in) that are carrying the parasite or eggs.

Symptoms of Internal Parasites (intestinal) in Betta fish: Though you cannot see the parasite, you will notice the Betta losing weight, despite a healthy appetite, due to the parasite stealing the nutrients.

Betta fish Internal Parasites (intestinal) Treatment: Do 100% water changes (75% in large tanks) daily, and thoroughly clean gravel or other substrate to remove any eggs or larvae. Treat with anti-parasite fizz tabs or pellets.


Description: Exophtalmia, a 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 fish: There are many possible causes including infection, rough handling or injury, gas embolism, tumors, or Vitamin A deficiency.

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

Betta fish Popeye Treatment: 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.


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 Septicimia in Betta fish: Infection of an open wound, or through ingestion.

Symptoms of Septicimia in Betta fish: 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.

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

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

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

Swim Bladder Disease (SBD or Bloat)

Description: 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 fish: Can be caused by damage to the Swim Bladder through injury, or by pressure from constipation.

Symptoms of Swim Bladder Disease (SBD or Bloat) in Betta fish: 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.

Betta fish Swim Bladder Disease (SBD or Bloat) Treatment: If bloat is present, treat the constipation with the inside of a pea and/or fasting. If injury is suspected, it should heal over time.


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

Symptoms of Tuberculosis in Betta fish: Lesions, loss of scales, extreme weight loss and deformation of the skeleton.

Betta fish Tuberculosis Treatment: 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.

Velvet, or ‘Gold Dust Disease’

Description: 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 fish: 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, or ‘Gold Dust Disease’ in Betta fish: 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.

Betta fish Velvet, or ‘Gold Dust Disease’ Treatment: 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.

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.

Happy fishkeeping!​

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