The Most Common Betta Fish Diseases: Causes, Symptoms and Treatments

Dr. Mollie Newton
Published by Dr. Mollie Newton PHD| Senior Editor
Last updated: April 8, 2024
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Betta fish are incredibly beautiful creatures that make a wonderful addition to a home aquarium for any enthusiast. Their bright colors, communicative behaviors, and relatively simple upkeep make them an excellent option for those with a moderate level of expertise.

For someone looking for something more interesting or challenging than the average goldfish, it’s still important to note that betta fish diseases are a real concern in any aquarium.

If you’ve ever wondered what to look for in an affected fish, or how to spot when a healthy betta isn’t doing its best, read on for more!

Article Summary

  • Common signs of a sick betta fish include changes in color, damaged fins, altered appetite, inactivity, gasping for air, rubbing fins on the tank, swelling, enlarged eyes, the presence of pus, erratic swimming, and more.
  • Proper diagnosis and treatment are essential, and it’s advised not to use medications without professional guidance.
  • Treating betta fish diseases often involves maintaining proper water quality, diet, and providing a calm environment, and quarantine tanks can be used for observation and recovery.

Some Betta Fish Background

Blue and Orange Betta
Blue and Orange Betta

Also known as Siamese Fighting Fish, the Betta splendens that many know and love has an undue reputation as an aggressive tropical fish.

Wild bettas were first found in the warm water of Thailand and eventually made their way to the domestic market in the mid-1920s with the explosive growth of hobby aquariums.


Captive bettas bear little resemblance to their wild counterparts, having been changed through captive breeding over many generations into the beautiful creatures we see today.

Fighting Fish

In reality, it is primarily the male betta fish that earns this reputation as a fighting fish, defending its territory with vigor and battling other fish during breeding seasons.

Male bettas are quite the fin nippers, and will use both a display of fin and gill expansions and actual combat to get their way.

A fish with its fins nipped may have trouble swimming, and more dangerously may appear to be injured when actually sick with a disease such as fin rot.


As a general rule, any pet fish suspected of disease such as fin and tail rot or swim bladder disease should be immediately placed in a quarantine tank for observation.

Betta fish are an adaptive, hardy fish when it comes to tank size and can tolerate conditions from a tiny bowl up to a larger tank system.

Is My Betta Fish Sick?

The first step in determining whether your betta fish is sick or not is to note if its appearance differs from the norm.

If you closely monitor your healthy betta fish, you’ll have a better awareness of when something is wrong versus what can be classified as normal behavior.

It should be noted that all of these signs and symptoms apply to male as well as female betta fish.

Signs of a Sick Betta Fish

Sick Looking Betta
Sick Looking Betta

While it’s important to note that there are a wide variety of symptoms that may not be outwardly visible when something is going on with your betta, there are some very noticeable ways to tell that something is wrong. These visible signs include:

Color Change

In most cases, you’ll notice illness in your betta as your fish appears to pale, or lighten in color.

The color producing cells in your bettas body won’t have the energy to properly show their fullest, brightest sheen and will appear duller than normal.

Additionally, the betta’s head may appear to be a different color altogether from its body, indicating that something is amiss.

Damaged Fins

While betta fish are known to be aggressive and can often come with preexisting fin and tail damage, seeing clamped fins, tail rot or receding fin edges is a sign of something more concerning.

Mild fin rot can very quickly progress into your fish losing the ability to swim entirely, as the bacteria present on the betta fish fin and tail wear the tissues away over time.

Change in Appetite

Another reason that it is important to keep tabs on the regular comings and goings of your betta fish is so that you can notice things like a change in appetite.

If you know that your fish is typically a slow eater, it may not seem unusual for it to take some time with its food.

On the other hand, if you know that your fish is a regular eater and you notice it ignoring or not eating food, you may have a sick betta fish on your hands.


Most betta fish diseases will leave your fish tired and struggling to remain active.

You may notice that your betta is sitting at the top of the betta tank, or laying along the bottom of the tank.

Sometimes we can mistake a sick fish for a sleeping one, but if your betta fish remains inactive for longer than several hours after it would normally be awake you may begin to suspect bacterial infection or illness.

Gasping for Air

Betta Swimming Towards The Water Surface
Betta Swimming Towards The Water Surface

A symptom of many common betta fish diseases and fungal infections of the gills, gasping for air indicates that your fish is not getting adequate oxygen.

There may be a fungal infection around the tissues of the gills, or a parasite such as Dactylogyrus preventing their proper function, or the conditions in the entire tank itself may have reached levels where there is no longer enough dissolved oxygen for your fish to breathe.

Rubbing Fins on the Fish Tank Itself 

A sign of fungal infections leading to fin rot or tail rot, your fish will attempt to rub off the afflicting agents off onto the fish tank.

It may run along the substrate of the betta tank as well, but either way, this is a sign that something is not right with the fish.


Seeing a betta fish with a swollen stomach is a definite cause for concern.

This may be a sign of constipation, fungal infection, or bacterial illness that is causing either gasses or undigested food to accumulate inside of the fish.

This bloated look is not only uncomfortable, but it can also mean that your fish is in danger of potential death.

Enlarged Eyes

Swollen eyes are a sign of infection and suggest that something has gotten into the tissues around the eyes or head, or even a mouth fungus (fish fungus) may be suspected.

Your fish may be in danger of losing one or both eyes, and precautions need to be taken to prevent further spread.

  • Puss – As with human wounds, puss is a sign that the betta fish is fighting off an infection. Puss itself indicates that the white blood cells within the fish are doing their best to fight off some form of outside intrusion and that your fish may likely need medical care.
  • Erratic Swimming – In contrast to lethargy, swimming in irregular ways can be a sign of distress or illness. Seeing a fish swimming sideways, upside down, rapidly, or at the surface can all indicate that something is going on with your fish.

How to Cure Betta Fish Diseases

Betta In Small Display Tank
Betta In Small Display Tank

For many diseases, treatment can be as simple as ensuring proper water quality, diet, and a calm space for your betta fish to recover.

The use of a separate quarantine tank or hospital tank with quiet space and comfortable lighting can go a long way towards promoting healing from quite a few fish diseases.


One of the subtle but ever-present dangers for a fish in recovery is stress. Your betta’s body will be doing its best to fight off whatever disease or infection is assailing it, but adding additional stressors such as light or noise can make this process much more difficult and drawn out.

If after a day or two things have still not progressed, it may be time to switch to something more hands-on and drastic.

Consult your home fish store, breeder, or veterinarian on the use of proper medications for your betta’s illness before attempting to fix anything on your own.

The Bath Technique

A good technique in your betta fish first aid kit, the use of salt to aid in fighting off a bacterial or fungal infection is a good one.

While referred to as a “bath,” this technique is more used to assist the entire aquarium system with ammonia poisoning or disease control.

Type of Salt To use

When we refer to salt, we typically think of table salt, or NaCl.

While this may be more readily available, it isn’t the best choice for our home aquarium as it often contains iodine and anti-caking components that can make it potentially harmful for your betta fish.


As it can act as a natural laxative for your betta, an epsom salt bath can be a good way to help them pass any undigested materials out of their system. Therefore we recommend epsom salt baths as a safe way to help fight off infections and diseases such as dropsy.

How to Perform a Salt Bath

  1. Measure out one tablespoon of salt per gallon aquarium water.
  2. In a separate container, dissolve the salt in a small amount of the water from your aquarium.
  3. Slowly add this solution back into your main tank.
  4. In the following week, continue to perform your regular 25% water change to return your salinity to normal. Do not add any additional salt after this point.

Here’s another way to do a salt bath without needing to mix the salt solution to your tank.

Salt bath treatment for Betta fish

Common Betta Diseases

While this is by no means an exhaustive list, we’ve gathered some of the more common betta fish diseases, along with their symptoms and methods of potential treatment.

You may notice that several of the symptoms for each overlap, which is why it’s important to get a proper diagnosis from a verifiable source before leaping to conclusions.


When there is disease preventing proper digestion of food, or your betta has eaten something that cannot pass through its system it will experience constipation.

While constipation itself is not likely to be immediately fatal, if left untreated it can be incredibly painful and lead to death.

There isn’t usually any worry of transmission with constipation as well, as it’s typically more often than not due to something that the fish shouldn’t have eaten.

Treatment can include aquarium salt to induce a laxative effect, but other medications may be recommended.


The term dropsy comes from an old English medical term for swelling in the abdomen caused by gasses or fluids.

The “drop” refers to the way the belly of the goldfish appears to droop in appearance as it swells. Today it would more likely be referred to as edema, but either way, it can lead to serious health complications in fish.

Signs of a fish with dropsy include swelling around the eyes and belly, the presence of lesions, scale loss, or abrasions, and becoming lethargic, excessively tired and having difficulty swimming.

Cause of Dropsy

Dropsy is caused by a group of several bacteria commonly present in most home aquariums.

A healthy, unstressed goldfish can handle the presence of these bacteria without much problem.

Dropsy is treatable if caught early. Unfortunately, by the time the more serious symptoms of dropsy begin to manifest, it may be too late.


Treatment for dropsy can be difficult and require medications or the use of aquarium salt, but the best place to start is by removing the infected fish to a separate tank to prevent dropsy from spreading.

Fish Lice

An easily identifiable crustacean parasite that attaches itself to the fins of your betta fish, which can lead to a fin-rot like appearance.

These can be treated by removing gently with a pair of tweezers and applying an antiseptic to the affected area. Aquarium salt or copper sulfate may be recommended to prevent further infestation.

Gill Fluke

These are a form of external parasites that look like little blood worms attached to your fish’s gills. They display redness around the gills, and can lead to difficulty breathing, weakened immune system and death if untreated.

These can indeed spread from one fish to another, and the first step is isolating the fish followed by treatment with medication or by adding aquarium salt to the tank to flush them out.

Ich/White Spot

Caused by the presence of the Ichthyophthirius multifiliis protozoan, this disease presents as small white pustules on the body, fins, and gills of the fish.

While easily identified, the trick comes in working against the complicated life cycle of the parasite itself.

Here’s what ich looks like on bettas.

Betta Ich

The ich parasite goes through three main stages of life, called the feeding stage, the reproduction state, and the free-swimming stage.

Unfortunately the parasite is resistant to treatment in all but the last phase, when it is most likely to spread to other fish in the tank.

Infectious Disease

Due to its nature as an incredibly infectious parasite, rapid removal to a separate tank and the use of your betta first aid kit can help prevent the spread and save the fish itself.

Without additional hosts to spread to, the parasite should die out through raising the water temperature, using agents such as malachite green or aquarium salts, and giving your fish plenty of time to recover properly.


When the water in our fish tank becomes polluted by natural wastes the pH level lowers, available oxygen decreases, and harmful levels of chemicals such as nitrogen and ammonia can accumulate.

Water that comes from the tap and has been treated with chemicals may lead to excess nitrogen buildup.

Additionally, the breakdown of organic materials such as plant matter, fish excrement, and uneaten food can cause a rise in ammonia levels.

Signs of Ammonia Poisoning Includes

Red or bluish gills, clamped fins, tail rot, body rot, swimming at the surface, lethargy, shedding scales, and loss of appetite.

While preventing a polluted tank is the key to avoiding ammonia poisoning and dead fish, these events do happen.

Therefore, it’s important to know the steps to take when you suspect a poisoning in the tank.

  1. As much as a 50% water change
  2. Immediately changing carbon filters and filter media
  3. Test the water in the tank, if it has not improved try another 20% change
  4. Don’t feed the fish until conditions have returned to normal. A new cycle of feeding and excreting can send pollution levels right back to where they were.

Recognizing signs of ammonia poisoning is crucial for aquarium health. 50% water change, immediate filter replacement and knowing the frequency of changing filters, such as carbon filters, and regular testing are essential. Be patient and refrain from feeding your fish until water conditions have fully returned to normal.

Slime Disease

Many species of freshwater fish, including bettas possess a protective slime coat meant to shield them from the early stages of disease and infection.

Over time and with excessive damage to a fish’s scales, combined with poor water quality, this layer can break down.


As the excess slime produced from this disease tends to concentrate around the gills, you’ll often see the common symptom of your fish displaying difficulty breathing.

Seeing an excessively mucous-y fish, with what’s referred to as a stress coat covering it is a sign that the fish may have contracted slime disease.

While this may not be fatal to the fish immediately, it will be more predisposed towards further infection and the mucous coming off of it may transmit disease to other fish in your community tanks.

Swim Bladder Disease

Swim Bladder Disease In Bettas

Certain bacterial diseases can cause a swim bladder issue for a betta, causing it to swim sideways or even upside down.

The best treatment for a swim bladder disorder is to consult your local fish store for the proper medication, and to quarantine the sick betta fish in a separate tank so that the disease does not spread.

If you notice that your fish is struggling to swim, or seems like it is barely swimming, it may be an indication that a swim bladder disorder is at present and needs treatment.

Parasitic Infection

Maintaining a clean, safe environment is the first step to preventing a betta fish’s body from acquiring an infection such as velvet (also known as gold dust disease for the dust-like pattern it leaves.)

Viruses, fungi, and bacteria all thrive in conditions that vary ever so slightly from the ideal, meaning close attention to detail can pay large rewards for the diligent aquarist.

The general term infection can refer to a range of illnesses, fungal infection or a specific disease such as infectious protrusion disease or Ichthyosporidium, but most present in a similar fashion when considering the affected betta.

Signs of Infections Include

Redness, swelling, and lines of color radiating around affected scales,bleeding and possible ulcers, scale loss, tail rot, damage, or fraying, a change or darkening in color of regular scale and behavioral changes such as lethargy, swimming oddly, and appetite loss.

Treatment For Fungal And Bacterial Infection:

Quarantining the affected fish, cleaning and replacing the water in the tank, providing proper medication and antibiotics as needed, drying out suspected decorations carrying infectious organisms, and monitoring for further health complications.

Viral Septicemia

Betta With Fin Rot and Septicemia

According to the The Center for Food Security and Public Health at Iowa State University, Viral Hemorrhagic Septicemia (VHS) is a highly infectious, fatal disease caused by a viral infection spread through the urine or reproductive material of fish.

Contact from fish carrying the virus or objects in the tank can also lead to infection.

The infection can cause deadly hemorrhages, or excessive bleeding, in many different areas of the body of the fish.


Notable areas to check for bleeding include the base of the fins, eyes (leading to the classic “pop-eye” look), and abdomen.

However, affected fish may show no signs or symptoms until bleeding has progressed beyond help and can still be contagious to others.


As with many viral infections, treatment for VHS can be incredibly challenging, however the use of antibiotics and certain medications can be effective.

Isolate the infected fish immediately to prevent further spread and continue to monitor for improvement.

Tips on Treating Betta Fish Diseases

Sick Betta Fish
Sick Betta Fish

Consulting with appropriate authority is key!

Don’t just buy the first thing you see at the store that mentions whatever symptoms your betta fish may have and assume this will do.

Think of treating your betta fish like taking care of a child.

You’d want to know the entire extent of what’s wrong, rather than just jumping in to treat the immediate symptoms.

Correct Medication

Use the correct medications!

Never use anything that isn’t directly formulated for betta fish illnesses as a quick betta fix.

A veterinarian will be able to diagnose and prescribe the proper medication that is necessary for whatever specific illness or infection is ailing your fish, whereas a quick glance on the internet will tell you quite a few conflicting things about the same set of symptoms.


Remember that while many of these symptoms may be visible on the outside, there are still plenty of internal things going on that you may not be able to see getting better or worse. Assuming that you get medication from a reputable source, trust the directions and follow them fully.

Completing the Treatment Period

Finish the treatment period! As with any human medication course for bacterial infections, you want to use the entire treatment to ensure that it will be fully effective.

Cutting off a medication when a symptom has abated, rather than when the medication has reached its recommended effectiveness is a good way to have your healthy fish wind up sick all over again.

Preventing Betta Diseases

Betta in Blue Background
Betta in Blue Background

While all of the aforementioned diseases and bacterial infection can sound quite overwhelming and intimidating, there is still a lot that we can do before any of this occurs.

Preventing sick fish doesn’t have to be the bane of your aquarium existence! In fact, it can be as simple as keeping your well-filtered tank clean and keeping a close eye on proper maintenance.

Here are a few things to keep a close eye on in preventing disease in your tank:

Water Quality

Test your betta water and perform water changes regularly to ensure that there is enough oxygen and that the presence of harmful chemicals has not risen to dangerous levels.

There are many different test kits available on the market, which can show pH, oxygen, and ammonia levels.

If you notice the presence of floating particulate matter in your tank, it means that water conditions are not good!


Regular maintenance of your aquarium’s filtration system, including the filter media itself along with any accessory air pumps and stones, is key. Additionally, it would be best to clean and wash the betta toys and decorations of your aquarium while maintaining the filtration system.

Make a schedule for yourself and set reminders to perform these tasks so that they don’t get missed.


Make it fun, and include family members if possible so that the chore becomes something everyone can take part in and becomes less of a burden!

Check On Your Betta

Knowing how your betta normally looks and behaves should be the easiest part of keeping your aquatic pet healthy. Checking on them regularly will help bettas grow and stay healthy.

The more you familiarize yourself with the denizens of your fish tank, the better you can respond quickly and effectively if something changes.

Isolate Sick Betta

Betta in Mini Tank
Betta in Mini Tank

Even if you aren’t sure of what exactly is wrong, removing your betta from the main tank into a hospital tank such as a fish bowl is important.

Keep in mind that your fish will still require a minimum of a 3-5 gallon tank to remain comfortable, even if sick.

Quarantine New Fish

New aquarium fish are often a source of disease and external parasites such as anchor worms.

Take the proper time to isolate and introduce them slowly before putting them into the same tank with the rest of your community fish, in order to prevent the spread of disease and avoid shocking them with a change in conditions.

Avoid Overfeeding

Part of noticing the regular behaviors of your fish, be aware of how much food it actually needs. Overfeeding or a poor diet can lead to a bloated belly and constipation.

A good rule of thumb is to start slowly and wait 30 minutes after feeding.

If there is still uneaten food in the tank after this time, remove it to prevent the accumulation of harmful ammonia and nitrates as they break down.


Throughout today’s article, we’ve looked at a wide variety of betta fish diseases and bacterial infections, along with their causes, cures, and ways to prevent them.

One of the most important reminders is to always keep a close eye on both your betta fish and the water conditions in their community tank.

Most common diseases can be prevented through good betta fish care and maintenance and can be treated if noticed and dealt with quickly.

Feel Free To Share!

As always, we hope that you’ve found today’s post about betta diseases helpful in caring for your new betta fish.

Feel free to share this info with any other fish fanatics in your life, and we wish you the best of luck on your aquarium adventures!

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