Why Did My Betta Fish Die

There is nothing more disappointing than waking up to find out one of your fish has died. Any fish dying is sad, but even more so when you have to spend a good amount of money purchasing a beautiful fish like a betta. 

why did my betta fish die

In this article, we will be discussing some potential reasons why your betta fish died. We will be covering many areas of fish keeping such as water quality and disease.

Unfortunately, there is nothing you can do about the fish that has passed away. However, we hope these tips help you to find the cause of the problem to prevent this from occurring again in the future.

Introduction To The Tank

How you introduce your betta to the tank is important. You do not want to bring it home from the pet store and tip it straight into your tank. You need to give it chance to acclimatize to the water. 

Ideally, leave your betta float in the bag on top of the tank’s water for around half an hour before releasing it into the water. You will want to mix in some of your tank water into the bag to acclimatize your betta to the new water conditions.

Water Quality And Overfeeding

The most important part of keeping fish is ensuring that you have good quality water. This is a key part of keeping your betta alive and healthy. If you do not carry out regular water changes the tank’s water quality will be poor and potentially toxic.

Your tank must have a good quality filter. This will help to cycle your water and remove any excess ammonia, nitrite, and nitrate. High levels of ammonia are toxic to fish. 

If you have high levels of nitrite this can be equally as harmful and can cause your fish to contract diseases. While high nitrate is not as dangerous, if your filter is broken and these levels rise, your fish will become ill.

Ensure to carry out small water changes and clean out your filter regularly to help prevent a build-up of harmful chemicals. 

Always remove excess food and carry out water tests to ensure your levels are safe. Only put a small pinch of food into the water. If you overfeed your betta the rotting food will increase the ammonia levels in your tank.

Incorrect Water Temperature

In addition to a good quality filter, a heater is equally important for tropical fish. It is not recommended to keep a betta in cold water. You betta needs the water temperature to be between 75 to 80℉ to survive. 

Ensure that your heater is always on and buy a thermometer to monitor the water temperature.


Betta fish are commonly known as Siamese fighting fish and for good reason, they can become aggressive with other fish with flowing tails. It is essential to only keep one male betta per tank. If you place two in together they will fight until one is killed. 

Likewise, it is not recommended to place aggressive fish with a betta. As they have a long flowing tail and move fairly slowly, they are prone to be bullied. Fin nipping fish like angelfish and barbs should be avoided.

Only put your betta fish in a tank with small shoaling fish that are not aggressive, such as neon or glowlight tetras.


Stress is a big factor that can cause death in all species of fish. Like us, fish can be affected by stress, often rather severely. If they have had a stressful journey home or are being harassed in the tank, this can potentially cause death. 

There may be certain ornaments or plants that are stressing your fish out. Even the water pushed out by your filter or air stone can cause a betta fish to become stressed. 

If you see them puffing themselves out a lot, they may be able to see their reflection in the glass. They may assume this is another betta threatening them and become stressed as a result.

The best thing you can do is to keep your betta’s stress to a minimum by not disrupting or tapping the glass. Always ensure that there are sufficient hiding places in your tank.

Incorrect Tank Size

Your tank size is important. If you have a tank that is too small, the water quality will quickly become poor. A tank that is too small will not give the betta the quality of life it deserves.

Likewise, if you have a tank that is far too overcrowded, your filter will struggle to filter out harmful chemicals and this can potentially lead to your fish dying. 


Sometimes your betta may have a disease that you are unaware of. While you can do everything in your power to provide the best environment for your fish, sometimes death is due to disease.

While there are treatments for diseases such as fin rot and fungus, sometimes the illness is taken out of your control and you can only manage it, rather than treating it. 

To help prevent this, always make sure you are regularly health checking your betta for any signs of disease. If you notice anything worrying, pop to your local pet store to receive advice and potential treatment.

There are several different diseases that betta fish can be prone to. They may catch these diseases from other fish in your tank or from fish at the pet store. If possible, always treat your fish in a separate treatment tank to help any diseases from spreading further. 

In addition to the common fish diseases, bettas can potentially contract, they are also prone to tumors. Some of these can be treated if caught early. Always speak to a veterinarian if you are concerned about potential diseases.


We hope this article has helped you to understand why your betta fish may have died. These are the most common reasons and it is always worth looking into each issue individually before adding any more fish into your tank. 

A lot of fish keeping is trial and error and ensuring your water quality is good. While it may have been a one-off that your betta fish died, there could be underlying issues with your tank and water. Always speak to a trained professional if you have any concerns about your tank as a whole.