How To Tell If A Betta Fish Is Sick

How To Tell If A Betta Fish Is Sick: Common Reasons And Solutions

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It is always concerning when a pet becomes ill, but aquatic illnesses are usually a mystery to beginner to hobbyists and the signs go ignored. As a result, treatment is too little too late and the betta sadly dies.

Recognizing illness and disease early is easy and treatment is usually easy as well. The most important factors are being able to identify the disease or illness and knowing how to take calm, swift action.

Keep reading to find out everything you need to know about the most common ways your betta can become sick, signs and symptoms, and how to treat your fish if this happens to you!

Why do betta fish get sick?

Sick Betta

Underneath a microscope, your aquarium water is teaming with life, in both good and bad forms. Unfortunately, many harmful parasites, pathogens, and other microbes live undetected in our tanks, waiting to affect a compromised betta.

Fish get sick for the same reasons other animals get sick; their immune systems become compromised. This is usually due to poor water quality, instability within the system, or injury. 

As a result, their bodies are not able to fight off disease and illness and they contract a parasite, bacterial or fungal infection, or some other damaging pathogen.

But with so many different things that could wrong, how do you know exactly what is hurting your betta fish?

Luckily, there are many ways to determine the exact problem going on with your fish through observation, water tests, and eventually, experience. 

Why is your betta fish sick?

Now that we understand why fish get sick, let’s understand what’s going wrong in your own tank. 

In general, your betta fish is most likely sick due to unideal water parameters and poor water quality, tank setup, and/or stress. 

Water parameters and water quality

Good water parameters and water quality is the backbone of a healthy betta fish system. Betta fish tank water should always be 0 ppm ammonia, 0 ppm nitrite, and minimal nitrates (<40 nitrates) with a pH between 6.5-7.0. 

Any trace of ammonia or nitrite can lead to ammonia or nitrite poisoning respectively; excess nitrates can also start to affect fish after a while.

Significant deviations within pH can also be very harmful as the scale is logarithmic and increases/decreases more than the number value indicates. Remember, betta fish require a water conditioner to remove any chlorine or chloramine, which can quickly kill living cells within your fish’s gills and external body.  

More important than pristine water quality, however, is stability. 

Most fish, including bettas, cannot tolerate sudden, drastic changes in water parameters. This is why fish need to be acclimated before being introduced into a new system. Most often, this shock happens with water temperature.

Water temperature

Betta fish need a constant temperature between 78-80° F (25.6-26.7° C). They are tropical fish and their physiological processes work best in this range; too hot or too cold, and their bodies start shutting down.

However, say that you keep close to this range, but the temperature is constantly swinging throughout the day. This is almost as bad as having an unideal temperature to begin with.

Water temperature swings are stressful and can cause your fish to contract an illness or disease. Because of this, it’s always recommended to use an aquarium heater for stability. 

Tank setup

If your water parameters are good, then your tank setup might be lacking

Betta fish don’t need an elaborate setup, but they do need at least 5 gallons (18.9 L) of water to happily swim around; some hobbyists have made 2.5 gallons (9.5 L) work, but the more space the better.

As mentioned before, betta fish need an aquarium heater and filter (or daily water changes). They greatly appreciate decoration in the form of live plants and driftwood and don’t mind some tannins being added to the water.

Make sure that any decorations you choose to use won’t harm your betta in any way; coarse substrate can start to rip at delicate fins and some artificial plants can snag at or scrape the sides of your fish. 

Water flow

Water flow is also important to consider; while you need an aquarium filter to keep your betta fish healthy, too much water flow can start to hurt your fish.

Naturally, betta fish come from slow-moving and stagnant water. Their fins don’t allow them to swim against the current like some other fish can. As a result, they can sometimes be pushed around by the water current.

This can lead to bodily injury which can become infected and lead to further stress. 


Sick Betta Fish In Aquarium

Stress can be caused by all of the previous problems mentioned but can be the result of some other environmental reasons too. 

While not many hobbyists choose to keep their betta with other fish, some have docile bettas that have proven they can be kept in a community setting.

However, sometimes these pairings don’t last and the betta fish becomes aggressive. This can lead to excess flaring and chasing which can cause inflammation and fatigue and, possibly, some dead fish.

On the other hand, your community fish can also turn on your betta. Once-peaceful fish might start to chase and fin-nip at your betta. Of course, this can lead to ripped fins, which welcomes infection.

Other causes of stress could be lack of enrichment or over-flaring from the fish being able to see its own reflection.

If you notice that your fish is swimming up and down the side of your tank, this could be due to boredom. In this case, carefully rearrange the tank and/or introduce new aquarium-safe items into the tank to bring some excitement for your fish.

If you find that your fish is becoming aggressive and flaring up while facing the side of the glass, this could mean that it is seeing its own reflection which can lead to inflammation as well.

Failure to quarantine/acclimate

A healthy system starts with how you introduce fish into your tank. If you simply dump the bag of new fish into your aquarium without doing anything, you’re immediately setting yourself up for failure.

Ideally, you want to quarantine new fish for at least a month before putting them into a new tank; this is mostly the case if there will be/are other fish already in the system. A month will give enough time to observe any illnesses or diseases and treat them promptly. 

If your betta fish is the only one that will be living in the tank, you can simply acclimate the fish to the tank and let it go since the display tank can then act as the quarantine tank; this is not recommended if you plan on having live plants as some treatment methods are not plant-safe. 

Otherwise, you can float the fish for 20-30 minutes and slowly add water from the display tank to the bag or another bucket for up to an hour. This should help reduce stress and get your fish used to the parameters in your tank. 

Common betta fish illnesses: Signs and Symptoms

Now that we know what causes betta fish to become sick, what are some of the most common symptoms and illnesses you’re bound to come across?

If you’re lucky, you’ll only have to deal with one of these at a time. Unfortunately, some illnesses come along with others and you will have to treat two or more at the same time.

Don’t panic though! Take a deep breath and have a course of action. 

General signs

The general signs of illness are lethargy, discoloration, loss of appetite, labored breathing, and damaged and/or clamped fins. 

Unfortunately, many of the most common betta fish diseases share these symptoms and correct diagnosis can be difficult if you’ve never had experience with them before.

Ich/white spot

Ich/white spot disease is arguably the most common aquarium parasite (Ichthyophthirius multifilis) you will have to deal with in your betta fish tank. Luckily, ich is relatively easy to cure as long as you don’t panic.

The most obvious symptoms of ich are tiny white spots that cover the body and fins of the fish. You might also see your fish scratching against the glass and other objects in the tank as well as swimming erratically and flashing.

Ich is easy to cure with increasing water temperature and water changes, but can also be treated with dosing medication as well. For a full guide on treating ich, make sure to check out our guide here


Velvet is very similar to ich in behavior and appearance and is also a parasite (most often Oodinium spp. in freshwater fish). Unfortunately, velvet can be much more difficult to treat than ich.

Velvet will also cause your fish to develop small white spots across its body and fins; these spots are much smaller and look more like a dusting than the defined spots signature of ich.

This parasite can quickly cause your fish’s health to deteriorate, leaving them gasping for air and laying at the bottom of the tank. Because of how quickly it affects fish, medications are usually the best course of treatment


Columnaris is a bacterial infection (Flavobacterium columnare) that can cause great pain to your fish and needs to be treated immediately.

Common symptoms of Columnaris include fraying fins, lesions on the dorsal, cottony-growth near the mouth and gills, and compromised gill function.

Columnaris spreads very fast and is best prevented by quarantining new fish and maintaining water parameters. Otherwise, it will need to be treated with medications. 

Fin rot

Fin rot is not as bad as it might look and is one of the easier aquarium illnesses to treat. Fin rot tends to be more common in betta fish since their tails can get easily caught on decoration. 

Initial signs of disease are brittleness and discoloration in the fins; fungal cases of fin or tail rot might have white, fuzzy patches along the edges of the fins as well.

The easiest way to treat fin rot is through good tank maintenance and stabilizing water conditions. However, some hobbyists also turn to aquarium salt and other medications. 


Dropsy can be a difficult bacterial infection (Aeromonas spp.) to identify as most of the damage is internal and can be mistaken for constipation or pregnancy.

It is easiest to identify once the stomach has become completely bloated, leading to a drooping appearance. In extreme cases, the scales can start to point outwards like a pinecone

Sadly, dropsy is not easily cured and chances decrease dramatically from the time of diagnosis. The fish needs to be moved to a quarantine tank and treated with aquarium salt and/or antibiotics. 

Swim bladder disease

Swim bladder disease is also common in betta fish because they have a tendency to eat too much and can’t properly digest what they’ve eaten. 

The most common sign of swim bladder disease is erratic swimming or the inability to stay upwards while swimming. 

The best way to treat swim bladder disease is by temporarily starving your fish and then supplementing with a high fiber food, like de-shelled peas; water quality must also be maintained during this time.


A tumor is the last thing you want to find on your fish, but it is unavoidable for the most part and likely due to genetics.

Luckily, tumors are actually quite rare in fish, and a lump might not always mean the end of the world. Like humans, lumps can be caused by injury or infection and can turn into an ulcer or abscess.

For the most part, you don’t need to worry, and removing the fish from the tank would be the best way to go. From there, provide optimal care and monitor closely; with luck, the lump will start to go down in a few days. 

Keep in mind that a lump could also develop into one of the previous ailments as well if left untreated.

Unfortunately, if your fish does have a tumor, then there is not much you can do for it. Fish surgery is possible believe it or not, but most times, the cons outweigh the pros and at that point, it’s recommended to humanely euthanize the fish. 

Do betta fish play dead?

If your sick fish isn’t displaying any of these symptoms but is laying on its side and you are afraid it might be dead, don’t worry just yet.

Some animals play dead in order to trick predators to avoid entering a fight. However, betta fish do not.

Instead, they use their fins and gills to display dominance over the other fish. If one of the bettas refuses to back down, then they may chase after each other and attempt to bite fins and scales.

But what if you catch your betta fish laying on its side from time to time? While this isn’t particularly normal, it might not be something to start panicking over either.

Fish sleep. While they don’t sleep like other animals, they may doze off for a few seconds, leaving them barely swimming against the substrate or a decoration; bettas are especially known for sleeping on leaves and plants, which can definitely look like a dead betta!

If this seems to be happening when the lights are going out or are completely off, then there’s probably no reason to worry and it’s just your betta fish getting some shut-eye.

However, if you find your betta fish doing this during the daytime or a little too often for comfort, then you might want to start testing water parameters and checking for signs of illness.


Dealing with a sick fish can be scary. Luckily, aquarium-keepers have worked through trial and error for the past several decades to find out the best cures for the most common betta diseases and illnesses.

The first step is to not panic. Assess the problem as best you can and confidently treat for your diagnosis; sometimes you might be wrong, but luckily, most treatments and medications are effective for a broad range of illnesses.

If you have any questions about betta fish care, treating a specific disease in your own aquarium, or have had experience battling a particularly difficult case, don’t hesitate to leave a comment below! 

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