why is my koi turning pink?

Why is my koi turning pink?

Koi fish will turn pink for any number of reasons. Sometimes, they are closer to red than pink. Other times, they are more pinkish than red. Regardless of the color, the appearance of streaks, blotches, or spots on your koi fish should concern you because some of the potential causes are quite serious. They include:

1). Disease

[1] [2]

Even though koi fish are strong, they are still susceptible to a variety of diseases. For instance:

A). Bacterial Hemorrhagic Septicemia – causes streaks and open sores to appear all over the Koi’s body.

B). Pseudomonas Bacteria – Produces open sores of a pinkish or reddish color.

C). Carp pox – Produces a pinkish flush.

D). Fin Rot – If the fins and tails are the only parts of the body displaying this discoloration, the Koi fish might have fin rot. The fins of koi fish with fin rot will develop fuzzy growths[3].

E). Injury – Sometimes, pinkish/reddish ulcers develop on a Koi’s body because bacterial infections have invaded the site of a physical injury that the fish recently suffered. This is why aquarists are encouraged to treat wounded koi fish immediately

2). Water Conditions


Koi fish have a coating of slime that is supposed to protect them from harm. However, poor water conditions can degrade the coating, leaving the creature vulnerable to invasion from bacterial infections.

Koi fish require specific parameters in their water. The wrong conditions in their tank can lead to the manifestation of unexpected symptoms such as a pink flush. This includes temperatures that are too high, the wrong pH and hardness, and a small, overcrowded tank.

Pay close attention to the nitrates, nitrites, and ammonia. If your Koi fish is turning pink, the nitrate, nitrite, and ammonia levels are probably too high. If the creature is kept in a pond outside, you should consider the impact of factors like airborne pollutants and acid rain.

3). Food

Koi fish are popular because they are so colorful. However, some aquarists will attempt to enhance the appearance of their fish by giving them color-enhancing food. This practice is, for the most part, acceptable.

[5]However, if you give your fish color-enhancing foods like Spirulina in massive quantities, you could produce drastic changes in their appearance. For instance, white areas on their bodies will become pink.

4). Stress

Stress is one of the most common causes of discoloration in Koi fish. [6]Common sources of stress in Koi fish include poor water quality, an unbalanced diet, toxins and pollutants in the water, overcrowding, and aggressive neighbors, to mention but a few.

Besides changing color, stressed fish will jump out of the water, rub against objects in the tank, hide, lie on their sides, etc.

5). Sun


Koi fish have a slime coating that is supposed to protect them from elements like the sun. But that doesn’t make the koi fish immune to sunburn, especially if it lives in a pond. Some sunburns are more serious than others:

A). Minor sunburns will produce a mild pink rash. You should expect additional symptoms such as lethargy and loss of appetite.

B). Moderate sunburns will result in a deep red color. Lesions may appear.

C). In the most severe situations, the fish will develop blisters and ulcers. It may die.

6). Genetics

Some koi fish naturally change color as they mature. If your fish has developed a reddish or pinkish hue but it is completely healthy, you have nothing to worry about. The creature is simply manifesting the color it was always meant to have.

How to Treat Koi Fish that Turned Pink?

You have to match the treatment to the cause of the discoloration, for instance:

1). Diseases

You should talk to a vet. They will identify the disease ailing your koi fish and then prescribe an effective treatment. More than likely, they will recommend oxytetracycline (in the food) and Forma Green (in the water) for Aeromonas Hydrophilia.

Pseudomonas fluorescens, on the other hand, responds to Kanamycin and Neomycin (in the food). You can also use Forma Green (Water).

A Koi fish with blisters that have been imputed to Aeromonas salmonicida can be treated with Furazolidone.

Aquarium salt is often encouraged because some viruses and bacteria hate it. The salt will enhance the effectiveness of the drugs you have chosen to deploy. This is on top of encouraging the regeneration of the koi’s slime coating.

[8]Depending on the bacterial strain in your tank, you should think about raising the temperature to 82 degrees F. Salmonocida, for instance, cannot survive at temperatures that high.

Wounds should be cleaned and treated with antibiotics like Neosporin (ointment). Some ulcers will respond better to iodine.

None of these treatments matter unless you maintain a clean tank. Additionally, you shouldn’t forget to quarantine the diseased fish. Even if the creature has an illness like fin rot which isn’t contagious, the antibiotics used to treat fin rot could negatively affect the biological filtration capacity of the tank.

2). Water Conditions

Maintain the best possible conditions in the tank. Koi fish are large, reaching 36 inches in size. This is why you are encouraged to keep them outside in ponds. They need roughly 250 gallons of water per fish. Any pond used to store them should be at least 6 feet deep. This will allow the koi fish to survive in the winter even when the top of the pond freezes.

[9]They require a pH ranging from 6.0 to 9.0 and temperatures ranging from 74 degrees F to 86 degrees F (in a pond). In an aquarium, they prefer temperatures of 65 to 75 degrees F. You should change their water regularly. If they are turning pink, you should change their water immediately because they are most likely facing a spike in toxins.

[10]Install a filter that can process all the water at least three times in an hour. Invest in bacterial supplements that can control the waste in the tank. A koi fish living in a well-maintained tank is less likely to contract illnesses resulting from bacterial infections and parasites.

3). Stress


The easiest way to treat stress in koi fish is to maintain a conducive aquatic environment that has the right parameters. You should also take steps to cure the koi fish of any diseases that might be ailing them.

Eliminate predators. If they are housed in a pond, you can protect them from birds by either moving them to an indoor tank or using deterrents like nets, alarms, and sprinklers.

Don’t forget to add hiding spots. That includes plants like water lilies and hornwort and manmade shelters that can be installed at the bottom of the pond.

4). Sunburn

Minor sunburns can be treated by giving the koi fish shade. If the sunburns are serious, give the fish antibiotics. They might also require salt baths. Talk to a vet; they will recommend some effective medicated dips.

Koi fish that are recovering from sunburns should be fed high-quality meals. They need all the nutrients you can give them. The creatures are omnivorous. They can eat insects, algae, zooplankton, and commercial items with high protein content.

How Do You Know if a Koi Fish is Dying?

Some fish die quite suddenly, without warning. That isn’t the case with Koi fish. They display plenty of warning signs that will alert you to the fact that they might be approaching the end of their lives, including:

[12] [13]

1). Jumping

If your koi fish keep jumping, you should take that as a sign that they are greatly distressed. If your tank doesn’t have a cover, the koi fish could jump to their death.

2). Gasping

Fish that are gasping for air at the top cannot breathe. If you fail to remedy their situation, they will eventually die.

3). Lethargy

Some koi fish become highly inactive. They either swim at a slower pace than usual or they spend all their time at the bottom, lying in place. This is a sign that they are too weak to move. It could also mean that they are at death’s door.

4). Ulcers

Koi fish whose bodies are covered in open sores and ulcers are not a pleasant sight. But their appearance could also mean that they picked up a disease that is in the process of killing them.

5). Weight loss

You should pay close attention to koi fish that have lost an alarming amount of weight, particularly if they have also stopped eating. That is a sign that they are suffering from a severe, life-threatening illness.


1- https://www.nationalfishpharm.com/koipond/bacterial_disorders.html

2- https://koi-care.com/koi-diseases-treatments/

3- https://animals.mom.com/goldfish-ripped-tail-4408.html

4- https://www.angelkoi.com/copy-of-aeronomas-bacteria-1

5- https://modestfish.com/best-koi-food/









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