My koi appear to be losing their colour. What can I do?

I have just returned from my local koi dealer who has taken delivery of a shipment from Japan that included some magnificent 8-10″ Sanke. I didn’t buy any because I have some from the same breeder in my own pond. However, when I returned to compare my own koi, I was very disappointed by how poor the quality of the red appeared to be on my own koi compared to the newly imported koi at my dealers.

Coincidentally, my wife had also commented that the colours of my koi were not as vivid as they had been when I first introduced them and appear to have faded. I have read recently that a clear and filtered pond is not the best environment for koi, preferring the natural conditions of a mud pond. Is this why the 8-10″ Sanke in the dealer’s ponds were so vivid, having recently been harvested from a mud pond? What can I do to try and regain the vivid colours in my own koi and what may have caused their colour to fade?

I tend to agree with what you have read recently, that indeed the best environment for producing excellent koi health and colour is a mud pond. You might regard a typical filtered koi pond as a compromise between the conditions that we want for our koi (so we are able to view them in clear water) and the conditions that are the best for our koi’s health and colour. If we were in the business of providing Koi with the ultimate conditions then we would undoubtedly keep them in a mud pond – but we also want to see them and this compromise could well be the cause of the fading colours. The natural conditions in a mud pond provide koi with a constant, high-quality source of Carotenoids, which are the colour producing and enhancing compounds that koi require to display their vivid colours. The mud pond environment it is also packed full of minerals that support and enhance the overall health of koi as well as the pond itself.

There are a number of reasons why the colours of your koi may be fading, some of which we can intervene and respond to, but others which are not environmental, but merely a sign of ‘age’. The most likely cause is related to the Carotenoids available to them in their diet and environment, especially if all of your koi appear to be fading.

The colours exhibited by koi are seated in the skin which is living, and like other physiological characteristics of koi, is affected by changes to its environment.

a) Carotenoids.

Koi and other pondfish are only able to exhibit pigments if they receive them (or their pre-cursors) in their diet. Pigment cells in the skin store carotenoids (a group of natural pigments) relative to the type of pigment cell. For example, a black pigment cell will store black pigment, red cells – red pigments and so on.

Carotenoids are provided in the diet, and koi can manipulate and change a number of pigments in the diet to those expressed in their skin. In a mud pond, koi obtain carotenoids from animal and vegetable matter that they consume when browsing on natural flora and fauna – Hence the unparalleled success of a mud pond. As this is not possible in the typical highly filtered koi pond, carotenoids must be provided in the diet we offer. Ensure that the food your koi are fed has a good balance of natural and artificial colour enhancers that can provide your koi with sufficient quality and quantity of colour enhancers. Look out for foods that contain colour enhancing ingredients such as spirulina, paprika, marigold etc. These natural sources of pigment contain a wide range of carotenoids that koi can manipulate into those that they express in their skin. Some koi foods also contain the precise pigments (astaxanthin, canthaxanthin) that koi can store directly in their colour cells (chromatophores).

Learn from the professionals. It is very rare for the colours of koi that are farmed in natural mud ponds to fade. What is the reason for the success enjoyed by the professionals? -Ponds with a clay-rich substrate and a high and complete mineral content and copious amounts of natural livefood. Excellent for health, growth and colour, but not for viewing!

Besides their food, other environmental factors that could be causing the colour to fade in your koi include:

b. Water Chemistry

The chemistry of a particular pond water may lead to fading colour through their being a deficiency in specific minerals.

Pond water that is ‘tired’, and has not been changed for some time, can have a tendency to become acidic through the interactions of the biofilter. Specific minerals can also become depleted as they are taken up and utilised by fish and other pond organisms and not being replenished. Studies and experience have shown that skin quality and colouration (especially white and black areas) in koi are enhanced when koi are kept in hard, alkaline water with a comprehensive breadth of minerals. Skin quality can be enhanced by the addition of montmorillonite clays that release a complement of minerals into deficient water, leading to an improvement in colour.

c. Irritants (Disease and Poor Water Quality)

A host of bacterial and protozoan (single celled) parasites besides causing koi discomfort can cause colours to apparently fade. Koi can respond to disease (and other irritants such as poor water quality) by secreting excessive quantities of protective mucus as a protective mechanism. A very simple globular protein, mucus can give koi and other pond fish a whitish hue when it lies on top of the skin. If on close inspection, excessive mucus is the apparent cause, then a simple skin scrape or water test should identify the likely cause of irritation, enabling remedial action to be taken. I trust this is not the case with your koi, but it may still be worth carrying out a skin scrape for confirmation.

Genetic Factors.

Unlike environmental factors, genetic factors that might affect koi colour are fixed and regulated by the koi’s own genetic make-up. These genes determine how the pattern will develop, as well as the quality of the pigmentation and skin quality.

How Koi Colour Changes with Age

One of the most fascinating aspects of keeping koi is watching how their appearance develops over time. Koi do not remain visually static; their patterns and colours evolve as they mature. It’s quite normal for new areas of pattern to appear, and equally common for minor imperfections such as shimis — small black specks on the skin — to develop as the fish ages.

When discussing koi colour development, it’s important to understand one key principle: genetics dictate the outcome. The intensity of red (beni), the depth of black (sumi), and the clarity of white (shiroji) are all largely determined by hereditary factors. No food, supplement, or pond treatment can fundamentally override a koi’s genetic programming.

Why Do Some Koi Fade with Age?

In ageing koi, colour change is often linked to the natural decline of pigment cells. As koi grow older, cellular efficiency gradually decreases. The specialised chromatophores — the cells responsible for producing and holding colour — may begin to underperform. When this happens:

• Strong reds may soften into orange

• Deep blacks can lose intensity and appear grey

• Overall contrast may reduce

This process is a natural part of ageing koi and should not automatically be seen as a husbandry failure.

Can You Prevent Koi Colour Fading?

While you cannot alter genetics, you can influence how well a koi expresses its potential. Maintaining excellent water quality, providing balanced nutrition designed for colour support, and minimising stress all help koi maintain vibrancy for as long as possible. Good husbandry won’t change the blueprint — but it will allow the fish to perform at its genetic best.

Ultimately, some koi will retain rich, deep pigmentation throughout their lives, and a select few will even improve with maturity. These are the individuals prized by serious enthusiasts. For the rest, our responsibility is straightforward: provide optimal conditions and allow them to age with dignity.

In koi keeping, patience and proper care matter far more than quick fixes.