The betta in your tank may have a hardy reputation, but that is never a reason for neglect. As pet owners, it is your responsibility to take good care of your aquarium fish, protect it from disease and give it the best, healthy life possible.

The betta fish, also Betta splendens or Siamese fighting fish, gained its notoriety probably because of its natural habitat as well as its labyrinth organ. In the wild, it lives in oxygen-depleted shallow ponds, streams and rice paddy fields. It could survive tough conditions thanks to its specialized organ that allows it to breathe air directly from the surface of the water aside from using its gills. However, these do not make your pet immune to betta illness, and thus you must look after your fish dutifully.

Symptoms of betta fish diseases

As you spend time with your betta, observing it in its tank, you will know its distinguishing characteristics and familiarize yourself with its behavior. One day, you might notice that your fish is acting rather odd, and leave you wondering if it is suffering from some common betta fish diseases.

You may spot symptoms of betta illnesses through the fish’s appearance. Its colors, once vivid, may fade. Growths or abnormalities in your fish’s body may be evident such as lumps, bumps or tears on its fins and tail as well as the presence of white spots. A sick betta may also have clamped fins. Betta diseases may also manifest as lesions on its skin and body. It may also have bulging eyes, inflamed gills and an enlarged belly.

A fish’s activity may also show symptoms of illness. Observe where your aquarium fish swims – in the middle, at the bottom of the tank or near the top? If it is swimming near the top of the tank, particularly if it puts its mouth at the surface, your fish might be in distress. Breathing problems could indicate betta disease. Symptoms may also include loss of appetite.

Perusing these, you may conclude that your betta is indeed sick. But do not hit the panic button just yet! The “first aid kit” you have at home is actually right under your nose – that is, simply correcting your betta’s living conditions. Check the guides below and you might just drive betta diseases away from your tank.

How do you treat a sick betta fish?

Before resorting to medication for suspected betta fish illnesses, these simple but effective tips for treatment will go a long way: check water condition, maintain the right temperature, put your bettas in a proper home, install safe tank decor and ensure your fish’s healthy nutrition.

Listed below are some of the priorities for you to take when treating a sick betta. However, if that information isn’t enough, you can always visit our guide on how to treat your sick betta fish

1.   Water Quality

If your betta looks like it is sick, the initial treatment is not as complicated as it seems. Veterinarians agree that the medication is right in front of you – the water in your fish tank!

Dr. Jessie Sanders, former president of the American Association of Fish Veterinarians, pointed to water quality as the no. 1 aspect of fish health as well as the top cause of diseases, repeatedly stating it in the website of her self-owned clinic, Aquatic Veterinary Services in California.

Poor water conditions in your tank is caused by waste which includes your aquarium fish’s excretions, its leftover food and even dead plant leaves. These are broken down by bacteria into ammonia, then to nitrate and eventually into nitrites which accumulate in the water and harm your betta.

Get a liquid-based testing kit to check that your betta’s tank is free from these toxins.

Common betta fish diseases such as fin rot or tail rot, a bacterial infection, are also caused by poor water maintenance. Even swim bladder disorder, tagged as a “fake disease” by Sanders, is a result of poor water conditions If you do not do your water changes periodically as needed, this stresses the betta and in turn, its buoyancy control is affected.

The treatment, then, is just through a little housekeeping – get a filter (low-flow to avoid injuring the bettas’ fins) for its tank and do regular water changes.. Water change, however, should be done gradually. Drastic water changes will lead to a sudden alteration in pH that may stress and even kill your betta. Dr. Jena Questen, member of the World Aquatic Veterinary Medical Association, recommends a 25 percent water change every two to three days.

If you use tap water, test it for heavy metals first and dechlorinate it. Heavy metals, as well as harmful chemicals like chlorine and chloramine, could cause severe illness to bettas.

2. Water Temperature

A fact about bettas is they prefer warmer temperatures, being a tropical fish and a native to Southeast Asia. Make your betta aquarium fish happy by installing a heater in its tank.

In the bettas’ habitat in Thailand, the temperature ranges from 27 to 31.5 degrees Celsius (81 to 89 degrees Farenheit) or an average of 29. 9 degrees Celsius (86 degrees Farenheit). As for its tank, you may keep it at 25 to 28 degrees Celsius (78 to 82 degrees Farenheit).

Too high or too low temperatures could weaken your betta fish’s immune system. A fish’s metabolism is also dependent on temperature, being an ectotherm. If the water in your bettas’ tank is too cold, they could not digest their food.

3. Bowl or Tank?

A small, cramped up space would do no good for your betta fish. In fact, its labyrinth organ that allows it to tolerate poor water conditions is only a “short-term survival mechanism,” as noted by Sanders.

A bowl will limit your betta fish’s normal swimming behavior. Without space for decors, your fish could not enjoy its hiding activity. Dr. Krista Keller, veterinarian at the University of Illinois Veterinary Teaching Hospital, recommended housing bettas in a five-gallon tank or larger, in an interview on the school’s website.

A small container accumulates waste easily. Housed in a proper-sized tank, an aquarium fish could live a quality life. A simple adjustment in your fish’s home could be key in the prevention and treatment of common betta fish illnesses.


4.    Tank Decorations

In beautifying your fish tank, choose decorations that will not harm your betta fish’s long, elegant fins. Ornaments, such as rocks, should not have sharp edges that could injure its body. Plants should also be trimmed regularly so your betta could rest under them safely. A healthy betta needs a comfortable tank to live in.


5.    Proper Diet

If your betta has a large lump on its belly, you might be overfeeding it.

A betta fish’s stomach is about the size of its eyeball. Considering this, feed your bettas just the right amount that would fit in their tiny eye-sized stomach and which they could also consume within three to five minutes. Food that sinks at the bottom of the tank should be removed to avoid waste buildup.

Bettas should also be fed with a balanced diet containing 35 percent protein. If their protein needs are not met, this affects their immune system, hinders proper development and leads to a decreased lifespan, reminded Sanders. Feed your bettas up to twice daily with a variety of betta-appropriate food.

If you are able to do all the aforementioned and still find your fish sick, it’s time to call an aquatic veterinarian and familiarize yourself with betta illness.

Common betta fish diseases

Common betta fish illnesses could stem from bacterial, parasitic, viral and fungal infections. It could also come from its environment (traumatic injuries from fish tank decors, and ammonia or chlorine poisoning), poor feeding habits and genetics.

Bacterial infection in bettas include fin rot, cotton wool or columnaris, and mycobacteriosis. Meanwhile, parasitic infections that affect a betta fish are ich (white spot), and velvet disease or gold dust. In general, a fish could acquire fungal infections from Saprolegnia, Branchiomyces and Ichthyophonus hoferi. From its environment, an aquarium fish could become ill from an excess of carbon dioxide in the water. Other diseases that befall a fish are eye disorders, lice, also a parasitic infection, and mouth fungus.

Fin Rot

Fin rot is caused by the pseudomonas fluorescens bacterium. Symptoms could start from a traumatic wound that gets infected. This could sometimes affect the betta fish’s entire body and not just the fins.

Fin rot or tail rot could manifest as the original injury or it could look like a raised pink, white or red spot on your betta’s fins.

The best treatment for this bacterial infection is to improve your betta fish’s environment. Test your water chemistry and do the regular maintenance of your fish tank. If persistent, this must be consulted with a fish veterinarian so they could clean or trim the infected area or administer antibiotic injections.

Fin rot is also often easily confused with trauma and general illness, and even among the misdiagnosis of owners who self-check their bettas, said Sanders.

Cotton wool disease

Cotton wool, among the common betta fish illnesses, is caused by Flavobacterium columnaris. Your betta may suffer from skin lesions with slimy or cotton like excretions due to this bacterial infection. Caught early enough, potassium permanganate is used as treatment as advised by the MSD Vet Manual. If not, antibiotic medication is prescribed.


Mycobacterium piscium causes mycobacteriosis, also among the common betta fish diseases. This highly contagious fish illness is the most common cause of death in bettas in breeding farms in Thailand, as stated by C.C.F. Pleeging and C.P.H. Moons on their paper on betta fish’s welfare issues.

Mycobacteria form granulomas or nodules within the tissues. Symptoms of this bacterial infection include weight loss, skin ulceration and bleeding, paleness and skeletal deformity. Mycobacteriosis could affect humans, appearing as skin lesions.

Ich or White Spot Disease

Bettas could suffer from ich, a parasitic infection caused by the protozoa Ichthyophthirius multifiliis. The parasite attaches to the fish’s body and burrows into its skin and gills, resulting in cysts that appear as white spots. This parasite reproduces rapidly and is highly contagious so this must not be left untreated.

Chemicals which contain copper sulfate, formalin or malachite green may be used as medication upon the advice of a fish veterinarian. Simply adding aquarium salt, doing water changes and increasing temperature are used as treatment. Move the infected bettas in a quarantine tank first before treating and administering medication.

Velvet Disease

Among the betta diseases that are bacterial in nature, velvet disease is caused by the protozoa Oodinium sp. Also called rust or gold dust disease, this appears as fine yellowish spots or as a thin velvety film as the parasites attack the gills and skin. Symptoms also include loss of appetite, lethargy and a tendency for the affected fish to scratch against rocks and hard objects, according to the MSD Vet Manual.

These betta diseases, such as parasitic, bacterial or fungal infections, may be introduced to your tank via a new fish, so a quarantine tank must always be ready. An infected fish, once identified, must also be separated immediately. Treatment and medication could then be conducted.

As for fungal infection, the following are those that affect an aquarium fish in general and those you keep in ponds.



This fungal infection looks like cottony growths on the fish’s skin, fins, gills or eye s that are light gray in color. Remove any dead or decaying matter and clean your fish’s tank for prevention. Potassium permanganate is also the suggested medication.


Branchiomyces causes this fish fungal infection that leads to respiratory problems and death of gill tissue. This fungus is typically found in decaying material in the environment but infection is rare.

Ichthyophonus hoferi

This fungal infection is very rare and usually affects older aquarium fish. This is typically caused by infected raw fish food. This looks like a small black growth on the skin, according to PetMD. Symptoms include bulging eyes, loss of color, ulcers and cysts in internal organs. The infected fish may also look like it is swimming in unusual circular movements. Treatment is to add aquarium salt in combination with maintaining good electrolyte and calcium levels in the water. You may also adjust the temperature to 82 degrees Farenheit.

Sanitizing the tank and removing decaying matter are part of the treatment for fish fungal infections.

Other fish diseases

Its environment could also cause health problems to your fish. A high concentration of carbon dioxide in water can be toxic. A fish suffering in this water condition will look lethargic and unresponsive. Tests will show the tank water to be acidic. The MSD Vet Manual suggests vigorous aeration as treatment. This increases pH in the water and decreases carbon dioxide concentration.

A fish could also suffer from eye disorders. This is common, with the affected eye appearing swollen, enlarged (pop eye appearance) bloody, ulcerated or disfigured.

Pop eye is usually caused by trauma. Tank decors are not just injurious to your fish’s fins, but also to its eyes. This could also be due to a dysfunction in your aquarium fish’s kidney and gills. This makes the fish’s body take in excess moisture that could build up in the tissues behind its eye, resulting in a popped eye. This is another effect of poor water quality.

Fish lice, meanwhile, is a parasite that attaches itself to a fish’s body, penetrates its skin and feeds on its blood. Lice look like small, clear disks that lie flat against the skin. The fish will scratch its body against objects as it tries to remove it. 

Another bacterial disease is mouth fungus which looks like white lines or clumps around the mouth.

Swim bladder disease in betta fish, a misdiagnosis?

Sanders, in the Aquatic Veterinary Services website, clarified some fake fish ailments that one could read about on a quick search on the internet. This includes the swim bladder disease.

It said that swim bladder disorder is an “internet sinkhole.” The betta has a swim bladder, a specialized organ it uses to maintain neutral buoyancy in the water column. She added that whether positively buoyant (floating) or negatively buoyant (sinking), the top cause is poor water quality, stressing your betta and troubling its buoyancy control.

Aside from the “fake” swim bladder disease, she also mentioned that fish does not suffer from constipation.

Ask the vet! Yes, even your betta fish needs its doctor, too!

When your bettas are sick, the quickest solution would be to check the internet and diagnose your aquarium fish yourself. But while you could get a wealth of reliable information on betta fish illnesses on the web, nothing beats the knowledge and years of practice of the experts – the veterinarians.

As fish keepers, you may think that you are already giving your pet the best betta fish care, but the treatment on the hands of a vet is still unmatched. Fish disease should not be taken lightly. Ailments must not be left untreated and be subject to speculation. Treatment for common betta fish diseases should not be done through trial and error of unguided medication and treatment. With a vet, you could raise any of your concerns and questions on betta diseases. Simply buying medication without a fish veterinarian’s advice could even cost you more money without you getting the results you wanted for your betta.

Many different diseases in fish manifest in similar ways so it could be confusing and difficult to rely only on visible signs and symptoms. But with the aquatic veterinarian’s trained eye, they could conduct diagnostic tests and a thorough physical exam to identify the specific betta fish illnesses and give them the proper treatment and medication.

Prevention is always key. If caught early, betta diseases could be addressed easily. So call your fish vet right away or do what you can at home.

A healthy betta needs the best living conditions to avoid diseases, which you could do on your own by maintaining its tank through regular water change, putting it in a five-gallon tank or larger with a heater and a filter, choosing safe fish tank decor, feeding your fish a balanced diet as well as observing precautions by quarantining new aquarium fish. But after doing your part at home and your bettas still manifest symptoms of sickness, it is time to seek professional help and leave it to the experts – consult a veterinarian. 


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