Why is my betta fish turning brown?

In this post, we will answer the question “Why is my betta fish turning brown?”. We will list and discuss the most common reasons whys your betta is turning brown and how to treat and avoid some of them.

Why is my betta fish turning brown?

There are several reasons why your betta fish might be turning brown. The most common are:

  • Your fish is ageing;
  •  It has the marble gene;
  • It is suffering from nitrite poisoning, columnaris or fin rot.

They’re Aging

Simply said, one of the reasons that your betta’s colour is changing is that they are getting older. The colour of your betta’s scales may begin to fade as they grow older, much like your hair begins to fade as you get older. 

In addition to your betta turning brown, you may also notice that it is fading in general. So if you’ve kept your betta for more than a couple of years, this may be the reason why they’ve begun to turn brown. 

This is especially true if you haven’t observed any other signs of disease on them. You may simply have to accept that it’s part of the natural process of their growing older.

The Marble gene

Betta fish who has the marble gene has a colour-changing gene that causes them to change colour. The marble gene is co-dominant, which means that if it has been bred into the same line that your betta originated from, he will also have the marble gene. 

Consequently, if your betta is still young and you’ve seen that they’ve begun to look blotchy in certain regions, they may have the marble gene in their DNA as well. 

It should be noted that it isn’t much you can do to resolve this situation. To your advantage, the marble gene has the capability of changing the colour of your betta more than once. Because of this, it is very conceivable that the blotches will change colour in the future, even though they are now brown.

Nitrite poisoning

Another reason that your betta’s colour may be starting to fade is that it is being poisoned by nitrites. It’s unfortunate that as the ammonia levels in your tank rise, it’s just a matter of time until the nitrite levels in your tank rise as well. 

It is at this point that the blood in your betta begins to become brown, which can be seen on the surface of your betta’s body. If left untreated for an extended period, the blood will become unable to deliver adequate oxygen to your betta, resulting in their suffocating. 

In addition to turning brown, you may observe that your betta begins to gasp at the surface of the water, becomes sluggish, exhibits fast gill movement and brown gills, and occasionally prefers to be near water exits in the tank, among other symptoms.

What is the best way to cure nitrite poisoning? 

Fortunately, nitrite poisoning is completely treatable, and the sooner you recognise the problem, the better the odds of your betta recovering. If your betta is suffering from nitrite poisoning, the first thing you’ll need to do is do a major water change. According to consensus, removing around 50% of the water will remove a significant amount of nitrate from the tank, immediately improving the circumstances in which your betta is living. 

Also consider reducing the quantity of food you give your betta so that less waste ends up rotting in the tank and boosting aeration to further minimise the amount of nitrite present in the tank, as previously mentioned. 

Adding aquarium salt can also help to prevent methemoglobin poisoning in your bettas by preventing nitrite from being absorbed via their gills, which can be harmful to them. For this reason, if you’re going to add aquarium salt, you should use around 1 tablespoon per gallon of water in your aquarium.

Preventing nitrite poisoning 

As a result, it is not difficult to avoid nitrite poisoning from occurring in the future, and if you follow the procedures outlined below, you can ensure that this does not occur in the future for your betta. 

• Change the water regularly – The first step is to ensure that you are changing the water regularly. Depending on the size of the tank and the amount of stock in it, you will need to modify the water level. More frequent water changes are required for larger tanks with less stocking, and vice versa for smaller tanks with more stocking. 

• Check to see that you’re not feeding your betta too much — You should also check to make sure that you’re not feeding your betta too much, and when you’ve finished feeding them, remove any uneaten food from the tank. As a result, you will be able to limit the quantity of rotting waste that accumulates in the tank. 

• The last point to mention is that testing the water regularly will help you to detect when the levels of ammonia and nitrite in the tank are rising. If you can detect nitrite poisoning in its early stages, you may be able to prevent it from occurring in the first instance.


If you’ve noticed that your betta has been sick for a while and that their gills have begun to turn brown, they may be suffering from columnaris disease. Nonetheless, this is not the most prevalent cause of columnaris, as you may notice other indications of the disease before the gills become brown, which include: 

• White cotton-like growths on the ground. 

• Torn edges; ulcers and sores; chafing 

• Rubbing up against objects 

• The mouth will begin to deteriorate as the disease progresses.

How do you treat columnaris?

The therapy of columnaris is pretty straightforward; however, the sooner you begin treating your betta for columnaris, the greater the likelihood that your betta will make a full recovery. The following are the actions that you will need to perform to treat columnaris: 

First and foremost, if you keep your betta with other fish or plants, you should separate them into a quarantine tank to ensure that they are not harmed by the therapy. It will be necessary to gradually reduce the temperature when this has been accomplished. At a temperature of 75°F, columnaris will have a lot more difficult time surviving, and reproduction will be significantly more difficult. It is important to remember not to drop the temperature too quickly since this might lead your betta to experience temperature shock. 

Once the fever has dropped to an acceptable level, you should begin treating your betta with an antibiotic such as Furan 2. Adding aquarium salt to the water can help to reduce the amount of stress your betta is experiencing even more. If you give it enough time and follow these methods, you should see that your betta is beginning to make a complete recovery.

Columnaris prevention

Fortunately, providing your betta with the bare minimum of care can help to prevent them from developing columnaris in the first place. You should take the following precautions if you want to ensure that your betta does not become infected again: 

• Check to see if the tank is not being cleaned regularly. 

• Avoid overcrowding the tank and do water changes regularly. 

• Place any new fish you intend to introduce into the aquarium in quarantine. 

• Make certain that your betta is not in the company of aggressive fish. 

• Also, make sure your betta has well-balanced food.

Fin Rot

Fin rot is the last thing on the list of things that might cause your betta to start becoming brown. 

• In contrast, if your betta has fin rot, only the fins and tail will be becoming brown, while the rest of their body will remain white or light in colour. 

Fin rot manifests itself in a variety of ways, including the following: • Fins deepen in colour in addition to turning brown. 

• They will begin to look ragged, red, inflamed, and painful at the tips of the fins as well as the rest of the fins. 

You may also notice the following symptoms when fin rot spreads and gets more severe: 

• It is perilously near to the body that the fins have retreated. 

• You may observe that bits of the fin is starting to slide off the surface of the water. 

• The discolouration may begin to deteriorate to an extreme degree. 

Finally, if left untreated, you may discover that the fins have rotted down to the body, and in rare circumstances, even the body of the fish may begin to rot.

How to treat fin rot in bettas?

Fortunately, if your betta is suffering from fin rot, it is rather simple to treat, providing that you discover it early enough in the process. The following is a list of the steps you’ll need to take to treat your betta’s fin rot. 

• Firstly, if you are keeping your betta with any other fish or plants, you should separate them into a quarantine tank to ensure that they are not harmed.

• After you’ve finished, you may add aquarium salt or API Stress Coat to the tank to finish it off. 

• Furthermore, to increase the water quality in the original tank, you should make a water change in it. 

• If they are suffering from severe fin rot, you will need to take the following steps to save them: 

You should relocate your betta to a quarantine tank as soon as possible; however, you should also remove 100 per cent of the water from the tank this time around. Add API Stress Coat once more if you haven’t already, as it can assist your betta in growing their slime coat back, which will aid in their overall growth.

Finally, in the case of serious fin rot, a more thorough treatment regimen will be necessary. In addition to the items indicated above, you’ll need to utilise an antibiotic or antifungal such as Furan 2 or API pimafix to combat the infection (depending on what you think is causing the issue).


In this post, we answered the question “Why is my betta fish turning brown?”. We also listed and discussed the most common reasons whys your betta is turning brown and how to treat and avoid some of them.

If you have any thoughts or doubts, feel free to drop us a comment below!

Frequently Asked Questions (FAQs): Why is my betta fish turning brown?

What can I do to restore the colour to my betta fish? 

Constipation and light colouration may occur in your Betta if he is fed a diet that is mostly composed of fish food. He will return to his vibrant colour if you feed him a mashed, cooked pea to help things along. 

What is causing my fish’s colour to fade? 

If the water quality in your aquarium deteriorates, your fish are likely to get anxious, and they may even become more prone to disease. A stressed or unwell aquarium fish may not exhibit its best colours, and they may even fade in colour as a result of the stress they are experiencing. 

What is the cause of my betta fish’s pallor? 

Stress is the most prevalent reason for betta fish to lose their colour, according to aquarium owners who have observed this phenomenon. Bettas are extremely sensitive to temperature changes and do not adapt well to these changes, which is a typical source of stress.

What causes male bettas to lose their colour? 

Stress, old age, accidents, and disease are all possible causes of colour loss in your betta. It is also possible for Bettas to lose colour on their own, especially if they carry the marble gene. As long as there are no other indicators of sickness in your betta, you shouldn’t be too concerned about their colouration changing. 

Do fish lose their colour as they get older? 

A fish, like anybody else who has reached old age, will begin to show signs of discolouration in various regions of its body as the years’ pass. You will notice that its original hue will begin to fade over time. It’s also conceivable that the fish’s body begins to seem transparent at this point.


5 Reasons Your Betta’s Turning Brown – https://www.bettacarefishguide.com/betta-turning-brown/

Song, M. (2006). Caring for Betta Fish. Lulu. com.