Betta Fish Turning Red: 5 Simple Steps To Fix The Issue

Disclosure: When you purchase something through my affiliate links, I earn a small commission. As an Amazon Associate, I earn from qualifying purchases.

Most people see their betta fish changing color to black. However, when I saw my betta changing its color to red, I was a bit worried. Luckily, as time passed, I gained some knowledge of the situation. I also learned how to prevent it from getting worse, especially when an illness is involved.

Betta fish tend to turn red due to genetic and environmental reasons. Naturally, blue betta fish may turn red as they age, approximately at the age of two. However, there are cases when betta fish turn red regardless of age. That includes ammonia poisoning, lack of oxygen, and stress.

In this article, I will discuss why betta fish turn red and how to treat the issue once environmental factors are involved. For those of you who hurry, that includes testing the water pH, ammonia, nitrates, and nitrites, using the API Aquarium Testing Kit (link to Amazon).

Also Read: Stress In Betta Fish

Why Is My Betta Turning Red?

1. Genetics

Some betta fish naturally turn red as they grow. That is typical for blue betta fish, but some betta fish with other colors do it too. The genes that control whether a betta will turn red also control the color of their skin, fins, and eyes. 

That means that red bettas that turn red will have red eyes and fins as well. If you have a betta fish that changes color, chances are it is one of these naturally red bettas. That usually happens at the age of about 2–3 years old.

In addition, there are some red betta fish that change color without having a naturally red parent. That is because many fish change color throughout their life naturally. The most common examples of this are clownfish and guppies.

2. Ammonia Poisoning

Ammonia is a type of poison that builds up due to too many nitrifying bacteria and debris. If you have a heavily stocked aquarium and excess nitrifying bacteria, betta fish may turn red due to ammonia poisoning. 

That is because ammonia burns the betta fish’s gills, causing it to turn purple, red, or possibly even bleed.[1] Other signs of ammonia poisoning include the water becoming cloudy and the fish seeming sluggish.

Also, you’ll notice that other fish in your tank are suffering as well. Some of them will become darker in color, while others will seem pale. Some fish will swim at the top of the tank as they are gasping for air.[2]

3. Disease (Red Spot Disease, Hemorrhagic Septicemia)

Some diseases can cause red betta fish to turn red. One of the more common examples is red spot disease. That condition is caused by a fungus called Aphanomyces invadans. However, some bacteria might do that as well.[3]

As the name suggests, the fish will develop red spots and won’t turn entirely red. But, on the other hand, it can also cause fish to go utterly red if it gets bad enough. Red spot disease is a severe condition because it typically spreads quickly and can kill your betta fish in as little as a few weeks if it isn’t treated correctly.

Another condition is Hemorrhagic Septicemia, also known as Red Pest disease. That is caused by a bacteria called Pasteurella multocida.[4] Besides redness, other symptoms include bloat, erratic swimming, bulging eyes, and air gasping.[5]

Again, you should suspect that the disease is turning your betta fish red if other fish in the tank change that color as well. Also, if a disease causes red patches, the coloration will typically involve the fish’s body instead of its fins.

4. Stress (Aggressive Tankmates, Lack of Oxygen)

As we explained above, betta fish change color as a result of something they are feeling. That includes stress, which is caused by a wide variety of different things. The most obvious example of this is the brightly colored betta fish that turns red or purple when it’s angry.

You see this behavior in overcrowded tanks or when the betta fish shares its environment with aggressive tankmates, such as other betta fish. The betta fish will turn red to signal to its owner that it is unhappy.

Lack of oxygen also causes stress in bettas. You see this in stagnant water, when the tank has poor water circulation, or when the filter is clogged. Besides changes in colors, the fish will frequent the upper sections since they are more oxygen-rich.

What Should I do if my Betta Turns Red?

If you notice that your betta fish gradually turns red, you should first look at its companions. If only the betta turned red, and its general state seems okay, this is probably a natural process and genetics.

However, in case other fish show worrying symptoms as well, you should take action right away:

Step 1: Put the Fish in Quarantine

First, I suggest putting the fish in quarantine. This means that you should not let it touch any other fish for at least seven days, and preferably longer than that. That is crucial since bacterial and fungal infections can be contagious.

You can then elevate the temperature by 1-2 degrees F. That will help the fish combat potential infections. You can also use the API Aquarium Salt (link to Amazon). Add one tablespoon for every five gallons of water.

At this point, I suggest consulting an aquatic vet to help you adjust the proper medication. Try not to search for the answer on the internet since that could make the situation worse. If you have an expert friend who has an aquarium, it’s even better.

Step 2: Study the Water Parameters

In addition to the seven-day quarantine, you should also check for ammonia or nitrite levels in the original tank. For that, I personally use the API Aquarium Test Kit (link to Amazon). I like this bundle because it also checks the pH, nitrates, and nitrites levels.

If the ammonia is too high (above 0.5 ppm), you should do a partial water change. However, it is crucial not to replace the water too abruptly since the fish are now used to high ammonia levels. Drastic changes will stress them even more.

As a rule of thumb, change 15-25 percent of the water weekly. You need to decide what is the right amount for your tank. That is easy, though, since there are no hard and fast rules. Use the fish’s behavior as a guide.

The suitable pH for betta fish is between 6.8 and 7.5.[6] Keeping the water within that range will help your betta fight infections and prevent stress. If the water is too acidic, regular water changes will help. Also, consider diluting the tank by removing excessive tankmates and decorations.

Step 3: Eliminate Stress

As was mentioned earlier, the lack of oxygen can stress your betta fish, causing them to turn red. Luckily, that is an easy problem to solve. All you have to do is to place an air stone in the middle of your tank.

To oxygenate my tank, I use the Hygger Aquarium Air Stone Kit (link to Amazon). I love this bundle because it’s easy to use and impressively quiet. Also, it provides enough air to complete the oxygen cycle for a relatively large aquarium.

When it comes to betta fish tankmates, it is best to keep it minimal. That is because bettas are highly territorial. As a rule of thumb, keep one male betta fish for every 20 gallons of water.[7] You should also avoid mixing bettas with aggressive tankmates, such as cichlids.

Step 4: Adjust the Temperature

Betta fish require a temperature of 75 to 80 degrees F. The ideal temperature is one that is close to your room temperature. If the temperature in your room is below 75 degrees F, you can place a heater on the tank. 

It is also vital that the temperature remains stable. Consistent fluctuations will stress your betta, making it vulnerable to disease. That is why I recommend getting the Cobalt Aquatics Neo-Therm Pro Aquarium Heater (link to Amazon).

I love that device because it maintains a consistent temperature without risking burns. It is also compact, lightweight, and energy-efficient. The temperature controller is easy to use, and it works with virtually any tank size.

Also Read: Betta Fish Hiding Behind The Heater

Step 5: Return Your Betta to the Main Tank

After being in quarantine for a week, check if the fish’s condition is getting worse. If it looks okay, and the water parameters in the main tanks are ideal for betta fish, you may place the fish back in its original tank. At this point, the chances that the fish is sick are pretty low.

However, if you notice sluggish behavior and a deterioration in its general state, keep it in quarantine. If the fish is back in the main tank, monitor its behavior. Keep an eye out for any signs of illness: rapid breathing, lethargy, loss of appetite. If you see signs that something is wrong, place it back in quarantine right away.

What Does it Mean When Betta Fish Change Color?

When betta fish change colors, it usually means that it is either sick or stressed. That is especially true for bettas that turn red, black, or white. Therefore, if a betta fish changes colors, it is best to remove it from its tank and get it to your local dealer to diagnose the problem.

However, as was mentioned earlier, betta fish also change colors as they grow. The most common example of that is blue betta fish that turn red at the age of about 2–3, especially if they are a naturally red strain. That means there is nothing to worry about in this case.

To determine whether your betta is ill, I suggest checking for other signs. Besides color changes, sick bettas will present with lethargy, loss of appetite, and ragged fins. In extreme cases, the betta fish may even bleed.

What are Signs that Your Betta Fish is Dying?

These signs indicate that a betta fish is dying:

  1. Lethargy – You’ll see lethargic betta fish are either swimming at the top or sitting at the bottom, not moving at all. 
  2. Loss of Appetite – A betta fish that is dying will show no interest in food.
  3. Rapid Breathing – Bettas with rapid breathing will frequently gasp for air near the top.
  4. Bulging Eyes – Dying bettas usually have bulging eyes as a result of fluid leakage.
  5. Swollen Belly – The belly of a dying betta fish will be very bloated and swollen.

If you notice one of your betta fish is about to die, you should immediately remove it from its tank. Then, put the betta in quarantine. If the fish dies while in quarantine, you should not dispose of it. Instead, please take it to your local dealer and ask what caused the condition.

I also suggest checking other fish in the tanks to see if they caught illness as well. One of the reasons for a dying betta fish is infections, which can be contagious

Also Read: Why Is My Betta Fish Turning Black?


All in all, betta fish color changes are usually a sign of stress or illness. Therefore, keeping your betta healthy and happy is critical to creating supportive behavioral patterns. That will ensure good health for a long time. 

If your betta fish turns red, it is essential to put in quarantine and reduce stress. This will prevent many diseases from infecting the fish. Once you put it back in the main tank, monitor its behavior for signs of illness.

Also, ensure the water pH, temperature, and ammonia levels are in a suitable range for betta fish (the pH should be between 6.8 and 7.5, and the temperature should fall between 75 to 80 degrees F). The ammonia and nitrates should be around zero.