Why Do Koi Lose Their Color?

Koi carp can be some of the most visually impressive fish, with striking color and pattern combinations. Koi are renowned for their bright, vibrant colors, and the healthy koi will be bright in appearance, with crisp, clear colors visible across their bodies.

However, in some cases, koi carp may begin to lose their colour. It begins to fade, look dull or otherwise appear to be on the wane. This can happen over a long period of time or in some cases, very quickly. Suddenly seeing your koi lose its color can of course be very alarming for the koi carp keeper.

So why do koi lose their color? If you are concerned about your koi losing their color and want to know why this might be happening, read on to find out more…

Food quality

Koi carp need to be fed top quality, nutritionally complete foods in order to keep their colors bright and allow them to reach their full potential. Feeding cheap or sub-standard food is usually the most obvious culprit in koi losing their color.

Why do koi lose their colour?Assess carefully what you are feeding your koi and ensure that they are getting all of the vitamins, minerals and supplements that they need, particularly if you find that all of your koi are gradually losing their color rather than just one fish.


The color of koi changes gradually throughout their lives, and as young koi reach maturity, their colors and patterns can appear to be very different from those that they started life with.

If your koi are young or are not yet fully grown, age-related color changes are to be expected.

Water temperature

It may come as a surprise to many koi keepers, but koi actually display the brightest colors during cooler weather. When the weather is very cold, their colors will be less impressive, but if you compare the coloration of your koi in the height of summer to the cooler days of spring or fall, you will almost certainly notice that they are brighter when the weather is not so hot.


Stress can lead to a wide range of symptoms in the koi, including the loss of their previously bright colors. This is particularly true at times when koi are breeding, as the mating process and being pursued by the male fish is very stressful for your female koi, so you can expect their colors to dim somewhat while this process is underway.

Sickness and ill health

A dull appearance or the fading of your koi’s colors can also be a sign of ill health or sickness. If one of your fish looks under the weather then look more closely to see if there are other signs of problems.

Poor water quality, lack of oxygen and illnesses can all lead to a loss of colour. You should always monitor your fish’s health and your koi pond’s water quality and correct any problems quickly.

Learn more about koi carp…

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