Betta Fish Disease and Illness: Preventions, Causes, and Cures

Although most people do not think of disease and illness when it comes to aquatic life, Betta fish are no more immune to harm than other animals. There are many health-oriented issues that can ail Betta fish and most are preventable. However, sometimes fish do fall sick and it is important not to panic and rush to buy medicine to put in a tank. Diseases and illnesses can be identified, which makes figuring out treatment a more manageable task.

Bacterial Diseases

Bacterial diseases are diseases that are caused either internally or externally by bacteria. These diseases are common among aquarium fish predisposition to them include factors such as poor water quality conditions, stressful living conditions, hypoxia (when a whole body or part of a body is denied a proper supply of oxygen, temperature changes, and the handling and transport of fish. High amounts of bacteria, both good and bad, are normally found in aquariums. A lack of proper nutrition and traumatic injuries can also make it easier for an otherwise healthy fish to fall ill due to bacterial diseases.


The bacteria usually enter through an open wound, mouth, or gills. Commonly happens in stressful living conditions such as a high bioload, not enough oxygen, and over-crowding. The bacteria can live in the water for up to 32 when water hardiness if at 50 ppm or more.

Symptoms: Ragged and frayed fins, usually followed by skin ulcers within 24 to 48 hours. Identified by cotton-like fungus covering wounds. Gills may change color, becoming light or dark brown, and fish will breath rapidly as a result of gill damage.

Columnaris in a goldfish. Photo by

Cause: Bacterial infection.
Fatality: Infected fish will die between 48 to 72 hours if no effort is made to cure. This is a rapidly moving disease.
Cure: If the fish is still willing to eat, feed with food containing oxytetracycline. If unable to eat, treat with antibiotics. Medications such as Tetracycline are recommended as well as those including drug combinations of TMP Sulfa, Sulfa 4 TMP, and triple sulfa.  Increase aeration in order to help fish not suffer from gill damage. Also treat secondary fungal infections.


This deadly ailment is not a disease itself but rather a symptom of a disease. It is usually the result of kidney problems and appears to be contagious because fish in the same tank will share the same living conditions but most cases are non-contagious. Dropsy can be the result of viral, parasitic, and nutritional problems, especially vitamin deficiencies.

Symptoms: High swelling of abdomen, due to large amounts of internal fluid. Scales appear to stick outwards, like a pine-cone. Sunken eyes and a tendency to stay at the top of the aquarium are also common but less definite symptoms of dropsy.

A betta with pine coning scales, a symptom of dropsy. Photo by

Cause: Bacterial infection of the kidneys and viral, parasitical, and nutritional deficiencies also cause dropsy.
Fatality: Very High. Most fish that show signs of dropsy do not survive.
Cure: Can try medications aimed at dropsy or kidney failure, however, there is no known cure. Euthanizing fish to prevent suffering is common.

Enteric Redmouth (hemorrhagic disease)

This disease, more commonly known just as redmouth disease, is a bacterial infection that can occur in both freshwater and saltwater fish. Symptoms: Serious bleeding (hemorrhaging) from broken blood vessels inside a fish’s mouth, body, fins and eyes. Can be clearly seen as bloodshot appearance on fins.

Cause: Bacterial infection from the bacteria Yersinia ruckeri.
Fatalitiy: Low. Very treatable.  
Cure: Antibiotics such as ampicillin.

Eyecloud (cloudy cornea)

Symptoms: White, hazy, film on eyes.
Cause: Bacterial infection commonly caused by bad water quality.
Fatality: None. Can harshly impair vision.
Cure: Antibiotics such as Fungus Clear and Metafix. Also, be sure to clean and improve water conditions.

Fin and Tail Rot

Not to be confused with tail biting. This disease will slowly eat away at the fin and tail of a Betta fish and if it reaches the base, the fin and/or tail will not be able to grow back. It may also attack the fish’s body if left to worsen at this point. 

Symptoms: A ragged rotting of the fin or tail. Infected areas appear to be melting away.

A male halfmoon betta with fin rot. Photo by Google Image

Cause: Bacterial or fungal infection, sometimes with both together.
Fatality: Medium, depending on effectiveness of treatment.
Cure: Antibiotics specifically labeled for fin/tail rot, such as Tetracycline.


Symptoms: Open red sores, skin abscesses, and ulcers around sores.
Cause: Bacterial infection due to poor water conditions.
Fatality: Medium to high.
Cure: Antibiotics such as Fungus Clear.

Mouth Fungus

This disease appears to be fungal disease but is actually bacterial.

Symptoms: Grey or white line around lips, later as fungus-like short clumps around mouth.
Causes: Bacterial infection.
Fatality: Medium to high. Fatality occurs if not treated in early stages.
Cure: Antibiotics such as amoxicillin.

A betta with mouth fungus. Photo by

Pop Eye

This is another disease that is actually a symptom of a disease. The real cause is difficult to determine but can be generally guessed.

Symptoms: Swelling or bumps on one or both eyes. Eye may pop out of socket.

A male betta with popeye. Photo by

Causes: Could be viral, a tumor, parasitic, or tuberculosis infection.
Fatality: None to Low
Cure: Antibiotics such as Tetracycline

Fungal Diseases

Fungal diseases are usually secondary diseases that are the result of a previous health problem. However, such is not always the case. There are many fungus treatments that cover a wide variety or symptoms and disease, so treatment is not difficult. It is important to keep fish separated when fungal diseases are present, so a quarantine tank is recommended.

Fin and Tail Rot

Not to be confused with tail biting. This disease will slowly eat away at the fin and tail of a Betta fish and if it reaches the base, the fin and/or tail will not be able to grow back. It may also attack the fish’s body if left to worsen at this point.

Symptoms: A ragged rotting of the fin or tail. Infected areas appear to be melting away.
Cause: Fungal or bacterial infection, sometimes with both together.
Fatality: Medium, depending on effectiveness of treatment.
Cure: Antibiotics specifically labeled for fin/tail rot, such as Tetracycline.

Fish Fungus

Fish fungus is almost always a secondary infection, meaning that it commonly follows other infections such as an injury or bacterial infection. It often appears as white strings from external injuries. Eggs infected with fungus can infect other eggs with this disease.

Symptoms: Clumps of dirty, white, cotton-like growth on skin or fins.

A male veiltail betta with fish fungus. Photo by

Cause: Secondary infection.
Fatality: Low to Medium. Fatal if not treated relatively early.
Cure: Antibiotics such as Fungus Clear and Methylene Blue.

Parasitic Diseases

Parasites are one of the most common and problematic diseases for freshwater fish, especially betta fish. They are, as the name suggests, caused by parasites that can enter the water through the introduction of a new fish (which is why it is important to quarantine new fish before placing into community tank), contaminated water, and other ailments. They are treatable, like most diseases, and medication can be used but is only recommended if the problem is properly identified. Like with all diseases, try asking on an online community before treatment and care suggestions.

Anchor Worms

Anchor worms are commonly found in aquarium fish. While more common in cold-water fish such as goldfish and koi, it may infect other fish species such as Betta splendens as well.

Symptoms: Commonly attach to base of tail and/or fin as a worm-like extension. May also appear anywhere else on body. Swelling and redness may appear at site of extension.

A male veiltail with anchor worms protruding from his body. Photo by

Cause: Parasite infection. Can spread to other fish if new infected fish is introduced into tank.
Fatality: Medium
Cure: Antibiotics such as Parasite Clear and Methylene Blue.

Hole in the Head Disease

Symptoms: Fish will develop small pinhole-like abrasions at first. As disease progresses it will travel down the lateral line. May appear, as the name implies, like the fish has holes in its head.
Cause: Parasites. However, causes are sometimes debated.
Fatality: Medium to High Cure: Antibiotics such as Parasite Clear. Removing carbon from filter may also help improve condition.

Ich (Ick or White Spot)

This is one of the most common Betta fish diseases. The best prevention is clean, regularly changed, water kept at a steady tropical temperature as needed by this species. Although there are preventative medications specifically for ich and often pushed by stores onto consumers, this disease is highly preventable with proper care.

Symptoms: white spots appear on body of fish, generally with even distribution. Spots usually look like a grain of salt.

A male betta with very visible ich spots. Photo by

Causes: Parasitic infection.
Fatality: Low to High, depending on when treatment begins. Usually it is very easy to deal with. Cure: Antibiotics. Many exist specifically for ich but some recommended ones include Malachite Green and Fish-zole. Sometimes salt baths are also used in treatment.


Symptoms: appears to be gold or rust colored dust sprinkled on fish.
Causes: Poor water conditions, cold water, and stress leave fish susceptible to parasite
Fatality: Low to Medium. Very treatable.
Cure: First isolate fish, as velvet is very contagious. Parasite lives in dirty places, like gravel, so a 100% water change is a must. Clean tank thoroughly. Medicate fish and keep water conditions without fluctuation.


Some Betta fish healthcare issues are not diseases or illnesses. Here are some common problems Betta fish keepers face with their pets:

Lethargy (lack of energy):  Can be symptom of most diseases but may also be due to cold water. Make sure water temperature is between 72 to 85 degrees, preferably ranging from 78 to 85 degrees.

Not Eating: Most common with new fish, often Betta fish will not eat when introduced into a new living environment. They do this because they are adjusting to their new home and may be stressed. Behaviour usually lasts anywhere from a few days to a week. If the problem persists, try soaking food pellets in garlic water. Do not begin to feed bloodworms, as they are like junk food for betta fish and have almost no nutritional value while causing health problem if primarily fed. Some fish are very picky and will only eat flakes, in which case the best to get are ones easy to measure in size and leave the least mess so ammonia does not spike. Betta fish that are otherwise situated in an environment and stop eating may be exhibiting a symptom of a disease but it is important to determine what could be the cause as it is a common behaviour for multiple problems.  

Tail Biting: See article here.



Budiardja, Ray. “Fish Disease – Fish Medication.” Fish Supplies. Web. 6 May 2012.

F., Christie. “Velvet Disease.” Nippy Fish. Web. 08 May 2012. Merck. “Merck Veterinary Manual.”

Merck Veterinary Manual. Merck Sharp & Dohme Corp. Web. 06 May 2012. Merck. “Furunculosis – The Disease.” Merck Animal Health. Merck Sharp & Dohme Corp. Web. 06 May 2012.