Betta Fish Fin Curling – Common Causes and Fixes

betta fish fin curling

Betta fish are magnificent especially male bettas with long flowing and colorful fins, but what if your betta’s fins suddenly began to curl up? Could your fish be sick? Maybe it’s just normal!

A betta’s fins can curl up because of incorrect water temperature, poor water quality, diseases such as fin rot, and even old age. Alternatively, Fin curling may be a genetic, congenital disorder that will only become apparent at a certain age.

Make sure to check out our Betta Fish Care Guide And Species Overview.

Why Are My Betta Fish Fins Curling

Here are some of the most common reasons why bettas fish fins curl up:

  • Constantly swimming against a current – Although this phenomenon is rare, bettas don’t like strong currents, so try turning down your filter flow rate.
  • Betta fish fins can curl if the betta is stressed or traumatized – If your Betta suddenly starts to display fin curling, it could be because they are frightened or trying to protect themselves.
  • Wrong water temperature – Betta fish fins can curl up if the water temperature is consistently too high or too low for a betta fish. The ideal temperature range for betta fish is between 78-82° Fahrenheit or 26-28° Celcius.
  • Betta fin rot can cause fins to curl up – If your fish is suffering from fin rot or some other bacterial Infections, your betta’s fins will likely curl up and become ragged or mushy.
  • Poor water conditions can cause a bettas fins to curl High levels of ammonia are a good example of this and are quite commonly a factor. Perform regular water checks to rule this one out.
  • Genetic, congenital illness, or disease can be a cause of fin curling on your betta – This is a problem that would be present from birth but often unnoticeable until the betta has matured.
  • Old age is also a common reason for your betta fish to have curling fins – As betta ages, they generally lose color, and their fins become a little rough around the edges. This is quite normal, and some curling can occur.
  • Fighting and fin nipping can cause your betta frayed fins – Constant fighting can cause infections and stress and can lead to fins curling over or far more serious problems.

There is no single reason why betta fin curling happens. It isn’t easy to pinpoint the exact cause when it happens, but the list above can help you narrow down the cause.

Betta Fin Curling Close Up
Betta Fin Curling Close Up

Why Do Betta Fish Fins Curl

Apart from being a birth or genetic abnormality, why a betta’s fins curl is not widely known. The muscle fibers may weaken over time or during illness, causing the tips not to extend out fully.

Similarly, when fin rot strikes, there may be damage to the muscle fibers around the fin edges, or as the tissue dies, there will be no fibers to stretch out.

Fin curling in betta fish usually occurs when the fins have grown to a good length and isn’t usually noticeable with shorter fins.

If an older betta fish suffers from a birth abnormality or genetic defect, some or all of its offspring (fry) will likely suffer from the same defect, and it won’t often become noticeable until later in life, usually by 1 year of age.

Is Fin Rot Causing Betta’s Fins To Curl Up

Fin rot may be the cause if you notice your betta fins curling up, and the best way to diagnose this is to inspect the edges of your betta’s fin visually. Look for signs of ragged or uneven edges, loss of color, or a milky white and soft texture. These signs suggest that your betta probably has fin rot.

Betta Fin Rot Symptoms And Treatments
Darken Fin Edges Are A Symptom Of Fin Rot

I won’t talk in-depth about the cause and treatments for fin rot, but you can read my article What Causes Fin Rot In Bettas (Symptoms & Treatment Guide), where you can find out everything you need to know.

Once you have correctly diagnosed fin rot as the cause of your betta’s curled fins, you will need to treat it. You may notice afterward that the fin edges will become transparent, which is usually a sign of fin regrowth in your betta.

Can Stress Cause A Betta’s Fins To Curl

Stress is the cause of many problems in betta fish and directly impacts a betta fish’s immune system. Betta fish are often subjected to poor living conditions such as small tanks and dirty water, which can cause ammonia poisoning. Betta fish may also experience shock from temperature changes, bullying by other tank mates, or even bullying from an owner. All of these things can lead to betta fins curling.

Any sudden change in your betta tank’s temperature can cause stress to your betta fish, such as a malfunctioning or broken heater, or if you set your aquarium’s water temperature too high or low for extended periods, this can also stress your betta.

Below is a list of common factors that will often cause stress to your betta fish:

  • Incorrect tank temperature or sudden temperature changes.
  • Exposure to loud noises.
  • Changes of the Betta Fish Tank’s Water Parameters (Use test kits regularly).
  • Pollution in the Betta Fish Tank causes spikes in ammonia, nitrate, and nitrite levels (Use test kits regularly).
  • Exposure to irritants such as household chemicals or certain medications.
  • Bullying from other tank-mates.
  • Boredom, which can be caused by lack of decor or other tank-mates.
  • Incorrect food or poor diet which may result in malnutrition.

The list above is not exhaustive, but you can see many reasons why betta fish can become stressed.

Although it’s easy for Betta fish owners to assume that stress is nothing more than a sign of poor water quality, which they can easily fix, stress can be caused by many other things or a mixture of factors. Betta fish are very sensitive creatures, and even the smallest change in their routine can lead to stress and their fins curling.

If you suspect ammonia poisoning, you will need to test your tank water immediately with a test kit and perform a water change to help bring ammonia levels down. You will need to perform repeat water changes until you have zero ammonia in your tank and then.

Keeping a clean and healthy tank is paramount in maintaining a betta’s health. It would help if you understood when to clean your betta tank and how often to change the water in your betta tank.

Before I move on I would like to mention that Indian almond leaves are talked about quite often in betta forums as a good natural remedy for many betta ailments including stress. It has many antibacterial properties which are beneficial to your betta tank.

Take a look at the video below if you want to find out a little more about this natural remedy.

How To Use Indian Almond Leaf Extract

Age can play a factor in your betta’s fins curling over and is probably caused by a general weakening of muscle tissue. You will usually find curling fins in male betta fish because their plumage is much longer than female bettas.

When fin curling is caused by old age, you will usually notice the dorsal fin starting to curl because of the weight on top, whereas the ventral fins which hang below will remain straight due to gravity.

Often when curled fins are brought on by stress or illness, the ventral fins will also begin to curl. Age-related fin curling is nothing to worry about and may or may not rectify itself. Why not read my article – How To Tell If Your Betta Fish Is Dying Of Old Age which talks a little more about age-related symptoms in betta fish.

Betta Fin Curling Through Illness

Bettas are susceptible to many illnesses often caused by a lowered immunity from stress. However, not all illnesses are caused by stress. When adding new fish or plants into your aquarium, you may inadvertently introduce a parasite or bacteria which can spread through the tank.

Betta fish generally suffer from 4 main illnesses, which are:

  • Fin Rot.
  • White Spot (ich).
  • Dropsy.
  • Velvet.

Any illness that will make your betta feel under the weather may also cause fin curl, and the solution is to treat the illness with medication obtained either commercially through a pet store or fish store or medication obtained through a vet.

Aquarium salt is also used often in low doses to prevent or help soothe tail and skin issues.

Treatment Of Fin Curl In Your Betta

There is no one cure that fixes all treatment types for fin curl, so you will need to follow the guidelines throughout this article when trying to find the cause of the fin curl.

Once you understand the likely cause of the fin curl, you will better understand how best to treat it.

Fin curl caused by stress will require you to identify the cause of the stress. For example, bad water quality will require you to improve the water quality, or temperatures outside of the recommended range will need to be fixed.

It cannot be fixed if fin curl is caused by old age or a genetic or birth abnormality.

If your betta’s fin curl is caused by illness, you will need to correctly diagnose and treat the illness, which will sometimes require you to seek the advice of a professional.


Hopefully, this guide has given you a little insight into fin curl in betta fish, its likely causes, and how to remedy it.

Knowing that fin curl can be the symptom of an underlying illness can give you some awareness of an illness you may not have otherwise known about.

Understanding that fin curl may be genetic and a simple congenital disability can give you some peace of mind that your betta may not actually be unwell.

Realizing that stress can have a large part to play in many conditions, including your betta fish’s fins curling up, can help you spot the possible triggers for stress before further illness ensues.

Although these problems are fairly common, they are not often fatal, and the more you learn to spot the signs, the more successful you will be at raising not only your betta fish but any fish.

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Jon O'Connell

I have kept both marine and freshwater fish and set up almost 100 aquariums. Happy to share my knowledge and experience to help others enjoy keeping healthy and happy fish.

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