Why Is My Betta Fish Turning Black? (And How to Fix it)

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Betta fish that change their color is a known phenomenon. However, bettas that are turning black for no apparent reason might worry some fish owners. That even happened in my tank. Luckily, over the years, I learned why they turned black and how to approach the issue.

Betta fish typically turn black as they mature. That is primarily manifested in their fins, which slowly become darker as they grow. However, environmental factors may turn bettas black as well. These include inappropriate water conditions, stress, and infections, such as black spot disease.

In this article, I will cover the reasons that might have turned your betta fish black. Then, I will present a few simple solutions to reverse the issue (if environmental factors are involved). For those of you who hurry, the first step would be testing the water using the API Aquarium Test Kit (link to Amazon).

Also Read: Stress In Betta Fish

Why Is My Betta Turning Black?

1. Genetic Factors (Marble Gene)

The marble gene in bettas causes a subtle change in skin coloration with no effect on health. In general, a fish with this gene has a dark bluish tinge in the fins and tail. A fish that is showing dark shades on its fins may be due to this gene. 

This gene causes a change in the pigment that makes up the betta’s skin. If the betta has this gene, it may start to turn almost entirely black permanently. It is a dominant gene, so it will show up in the offspring of the affected fish. Although very rare, a fish with this gene may have a small amount of pigment in the fins and tail.

Bettas that carry the marble gene will typically darken at the age of two.[1] So if your betta is turning black and it’s under a year, it is probably not due to this gene. As the fish grows older, it will become darker and darker.

2. Inappropriate Water Conditions

Water conditions play a significant role in how healthy your betta will be. One problem is that many bettas are put into an unclean tank with poor water conditions. Therefore, the first thing you should do when you get a new fish is to test the water quality.

For example, ammonia poisoning may turn your betta’s scales black, as happens in goldfish.[2] Ammonia usually spikes in overcrowded tanks since it is a byproduct of uneaten fish food and urine. The same is true for nitrates and nitrites.

I also suggest considering the pH. If the pH is too high, or if the water is too acidic, it can adversely affect the health of your betta. The ideal pH for bettas should be 6.8-7.5, although the pH can be a little lower.

Another critical factor is the water temperature. Bettas thrive in temperatures ranging from 75 to 80 degrees F.[3] Consistent water fluctuations or water that are too cold or hot may stress your bettas. That, in turn, can lead to black shades.

3. Black Spot Disease

Black spot disease, also known as diplopstomiasis or fluke disease,[4] is one of the most common parasites that affect bettas. It’s a parasite that can be contracted from dirty water or overcrowded tanks. Bettas get black spots as the parasite burns through their skin. 

The parasite spends the first part of its life in the water and later attaches to the fins or body in bettas. It can also spread from tank to tank through water and nets. It usually appears as tiny black specks or dots on the body of the bettas.

Bettas that suffer from the condition will appear very lethargic, and skinny, and may lose their color. In addition, they will have a loss of balance and swim in erratic patterns. However, the most noticeable sign is the accumulation of black dots at specific locations on the fish’s body.

4. Stress

Stress can harm your betta’s health and coloration. In some cases, it manifests as black fins or scales. For instance, bettas kept in tanks that are overcrowded or have aggressive tank mates may show signs of stress

The most common scenario is too many bettas in one tank. As a rule of thumb, it is best to keep one betta for every twenty gallons of water.[5] If you keep your betta in a too-small tank, it will force unnecessary encounters and aggression. 

That is especially true for male betta fish. They naturally love to defend their territory and will fight off other male bettas. It may also happen when the bettas are kept with aggressive tankmates, cichlids in particular.

5. Tank That is Not Cycled

Bettas are most compatible with a cycled tank. Cycling is the process of establishing biological filtration in the aquarium, and it is essential for fish to live. In addition, bettas are very sensitive to ammonia poisoning, so a cycled tank will help keep their health in check.

Proper cycling typically takes 6 to 8 weeks.[6] Tank cycling can be sped up by adding beneficial bacteria to the aquarium using a bacterial inoculation product. However, you should avoid using additives that contain ammonia.

What Should I do if my Betta is Turning Black?

If you own a betta that is turning black, you should first eliminate environmental factors. Then, if everything checks out, it leaves you with genetics and natural growth.

1. Adjusting the Water for Bettas

To adjust the water for bettas, you should consider pH and temperature. As was mentioned earlier, the suitable pH falls between 6.8 and 7.5. You can quickly test it using the API Aquarium Test Kit (link to Amazon), which will also measure ammonia, nitrates, and nitrites.

I love this kit because it is easy to use and gives you a bunch of information simultaneously. The test strips are easy to read and give you a quick visual indication of the water quality. Within five minutes, you’ll know what happens in your tank.

If the water is too acidic, perform more regular water changes. As a rule of thumb, I suggest replacing 15 to 25 percent of the water weekly. Try not to make drastic changes at once. This way, your fish may be stressed even more.

As was already mentioned, the ideal temperature is between 75 and 80 degrees F. To achieve a stable temperature, I use the Cobalt Aquatics Neo-Therm Pro Aquarium Heater (link to Amazon). That is absolutely the best heater I have tested so far. No other device kept my water that stable.

2. Treating Black Spot Disease

If you suspect that your betta could have black spot disease, you should take him to a reputable fish doctor and have him tested to ensure that it is not some other type of disease. The good news about this is that treating black spots with medication can be very successful.

It would help if you also quarantined the fish. That way, you can be sure that it will not infect the other ones. If you wish to treat the condition on your own, you can use the Seachem ParaGuard Parasite Control (link to Amazon).

Another option is to raise the temperature by two to three degrees F. You may also use the API Aquarium Salt (link to Amazon). All you have to do is pour one tablespoon for every five gallons of water in the quarantine tank. That will work as a bridge before seeing a vet.

3. Eliminating Stress

Your first action here would be picking the suitable tankmates for betta fish. That includes fish like Kuhli Loaches, Ember Tetras, Harlequin Rasboras, and Cory Catfish.[7] It would be best to avoid fish like Angelfish, Oscars, Parrotfish, and male betta fish.

If your betta shares a tank with other tankmates, consider adding a few plants. Suitable ones include Amazon Swords, Dwarf Sagittaria, Pygmy Chain Swords, and Anubias. This way, you minimize unwanted encounters and provide the fish with hiding spots.

I also suggest diluting the tank’s population or possibly getting a bigger tank. Finally, consider adding a foam divider. This way, you can isolate the tank from other fish and provide them with a peaceful environment to swim and breed. 

4. Cycling Your Tank Properly

Before adding a fish to your aquarium, you need to make sure that the tank has gone through the correct cycling process. This is necessary to establish beneficial bacteria. They will eventually help balance nitrogen levels in the water. 

This means that ammonia and nitrite will be at an acceptable level. When cleaning the tank, try not to remove the filter’s media. This part contains beneficial bacteria that support your aquarium. However, you need to clean up any organic matter build-up.

As was mentioned earlier, a reasonable period falls between 6 to 8 weeks of cycling. But you can hasten the process by using commercial products, such as the API Quick Start Nitrifying Bacteria (link to Amazon). A few drops of this will get your tank ready.

5. Providing Enough Oxygen

Finally, bettas need sufficient oxygen levels. Unfortunately, they are sensitive to low oxygen levels, and thus it’s vital to provide your fish with an appropriate environment. The easiest way to do that is by using a water pump that circulates the water.

Another helpful way is to use an airstone. In my tank, I use the Hygger Aquarium Air Stone Kit (link to Amazon). I highly recommend getting this one because it is quiet, reliable, and easy to use. All you have to do is put that device in the middle of your tank, and it will take care of the rest.

How do I Get my Betta Fish Color Back?

If your betta changes colors due to genetics, it is impossible to get its color back. However, if your betta replaced its colors due to environmental factors, you can bring back its original shades by adjusting the water pH, temperature, and ammonia.

It is also worth mentioning that a newly acquired beta might lose color after a few days or weeks due to stress and anxiety. Although it will eventually regain its original colors, providing a peaceful environment will speed up the process.

Also Read: Betta Fish Turning Red

Do Bettas Get Darker as They Age?

Bettas get darker as they age, especially if they are kept in less-than-ideal conditions. However, it is also possible for healthy bettas to get darker due to the marble gene. This will be primarily expressed in the distal parts of their fins and is unlikely to darken their scales.

As they become old and approach five years old, bettas typically lose their color and become pale. The reason is that they are losing the ability to produce melanin. Of course, this happens when they age, but it also happens in certain stress conditions.

What Are the Signs that Your Betta Fish is Dying?

Bettas that are dying typically present signs like lethargy, swimming in erratic patterns, and a loss of color. In some cases, they may even lose their appetite and weight. If your betta has any of the following symptoms, it is best to seek professional help. 

Other symptoms include loss of balance and swimming in circles. Sometimes they will exhibit a loss of color and become extremely pale. You should always have an eye on your betta, and you should check its health regularly. 

If a betta shows signs of stress, the first thing you should do is check the tank’s water conditions. Bettas typically become stressed if the water is too acidic, too hard, or too cold. It’s best to help your fish out by maintaining a stable temperature between 75 and 80 degrees F.

Also Read: Why Is My Betta Not Moving?


Bettas that are turning black may be suffering from stress or even a disease. The good news is that the colors are likely to come back if you treat the condition properly. However, they could also have inherited specific genes and simply grown to the coloration.  

As a rule of thumb, you may consider cycling your tank, adding beneficial bacteria to it, and providing hiding spots for bettas. This way, you will eliminate environmental factors that are causing the fish to darken.


  1. https://pets.thenest.com/bettas-change-color-4520.html
  2. https://www.vivofish.com/goldfish-turning-black/
  3. https://home.adelphi.edu/~ve21375/Betta%20Fish%20Care.html
  4. https://en.wikipedia.org/wiki/Black_spot_disease_(fish)
  5. https://www.thesprucepets.com/how-many-bettas-can-be-kept-together-1378744
  6. https://www.firsttankguide.net/cycle.php
  7. https://www.aquariumcoop.com/blogs/aquarium/betta-tank-mates