koi4u-2011 facebook  koi4u-2011 hoogland
You are here: HomeKoi and HistoryStability of colours

Stability of colours

Understanding of koi coloration is still an inexact science. The aim of this article is to provide an overview of koi and to try and explain some of the mysterious changes you may notice in your own fish. Stability of colours is very difficult to predict because it may be influenced by a variety of factors. Some of these factors can be seen while inspecting the potential purchase, while others will be unknown to the breeder, retailer, koi specialist and buyer. These unknown factors will be described throughout the article. It must be stressed that to attempt an article like this and consider the changes of all varieties of koi it will be almost impossible if the changes in the Komonryu and Suminagashi, Shusui, Asagi and Ogon must also be taken into consideration. I will therefore concentrate on the possible changes associated with wagoi koi and in particular the Kohaku, Sanke, Showa, Utsurimono, Bekko, Goshiki etc., because it is in these varieties that aesthetically and economically, the most devastating changes will take place.

The colour seen on a koi is the effect produced by three colour pigments. These are contained within cells called chromataphores. The three pigments are red, black and yellow. A chromataphore only harbours one colour. Under a microscope the chromataphore resembles the roots of a plant. Tiny reflective spheres within the skin that complements the colour pigment are irridocytes. All of the colours we see on our Koi are a mixture of these components. For example orange is a combination of red and yellow chromataphores; brown is a mixture of black, yellow and red. I have never seen a colour plate in a koi that consists of just one type of chromataphore. It is therefore safe to assume that all colours displayed by a fish are a combination of chromataphores, creating the impression of a solid colour. If there are no chromataphores present the Koi will appear white due to the irridocytes. On the other hand, the position of the irridocytes within the skin affects its reflective properties. If they are on the surface of the scales the Koi will have a metallic appearance. If they are in the lower layers of the skin the fish will have a mat appearance. In some cases, a combination of the irridocytes and the chromataphores will produce reflective colours such as gold on the surface. Blue is unusual in that it is a result of deep lying black pigment with irridocytes in the middle of the layers of the skin. The irridocytes interfere with the light to give a blue colour. If the complexities of the mixture of chromataphores and the subsequent combination with irridocytes are taken into consideration, the challenges associated with breeding purple as well as green coloured koi is daunting.  

Just like the irridocytes, the chromataphores may also be positioned on the surface of the skin, immediately under the scales or deep in the skin. If the chromataphores are very dense the coloration will also appear dense. However, the position of the chromataphores affects the 'stability' of the colour. The chromataphores on the surface of the skin will often produce unstable coloration due to them being removed or because they spread as the fish ages. Those deep in the skin are more stable and less likely to break up. The ideal is to have the same, dense colour pigment in all layers of the skin. This results in both a dense and stable colour. The chromataphores, as mentioned, are cells that can only hold pigment and cannot produce their own colour pigment. Therefore the fish have to consume it. In the confines of a Koi pond there is insufficient naturally occurring pigment-holding foods available to satisfy the Koi's requirements, therefore it is important to feed colour-enhancing foods. As with all Koi food, it is important that the colour enhancing food given is of high quality to ensure that the pigments are in a form that the fish can absorb into its body. Pigments in the diet, carotenoids to be specific have a lot to do with the maintenance of colour. There are a lot of carotenoids in shrimp and fish meal and there are colour pigments in spirulina and canthaxanthin, a common additive in food. If colour foods are not given to your Koi, the chromataphores would not be filled with pigment and the Koi will look pale or poorly coloured. This can result in a Koi of high potential quality only looking mediocre. Feeding a colour food would greatly enhance the appearance of such a Koi - but could not make a poor Koi great. The secret in keeping koi and allow the natural colour development to take its course, is to feed sparingly and allow the koi to utilize only the amount of colour enhancers that is necessary to develop the colour over a long period of time, till maturity. If this is rushed, the koi will reach an artificial state of finish which it will not be able to maintain for the same length of time that it should have if the enhancement of colour was allowed to take its natural course.
When the chromataphores are filled with pigment, the excess is passed through the Koi in the faeces. It is possible to get white areas of the koi becoming pink due to a temporary build up of Erythrin. This pigment is not absorbed in chromataphores and will quickly disappear as soon as the amount of colour food given is reduced.

There are two types of Beni (hi or red) that will be encountered, namely a red based and an orange based hi plate. Both these types of red can normally be identified at a fairly young age in koi.

As the name implies, the red based hi plate will give the tosai an appearance of bright deep purplish-red and may easily swing the hobbyist to buy this beautiful young koi that looks almost the same as the champion koi that we notice in books and magazines. As the fish gets more mature the colour may become “hard” and will not have the lustre and refinement that is so appreciated in mature koi. It is said that this type of hi will deteriorate very quickly under bad pond management. As the koi develops it will seem as if the hi “bleed” into the white where the two colours meet. This type of hi also breaks up more easily, forming scattered hi marking that move away from the main hi plate (tobi hi). Also when the fish swims and the body bends, a white edge will be noticeable between the scales. A good quality koi will have many layers of colour deep down into the skin, therefore this red based hi should be avoided.

The second type of hi is the orange based hi plate. The young koi will appear orange and distinctly unfinished. Koi keepers in general avoid this type of hi because of the unassuming appearance. This orange plate is the preferred colour because under the correct management, it will be more stable and will deepen in colour with age. It will also be more refined and retain the youthful appearance for longer.

Because fish is placed in a mud pond purely for the accelerated growth, the development of colour is temporarily ignored. When a young koi is harvested from a mud pond, it will appear faded. The hi will be thin and orange, the sumi will be grey and the shiroji will be creamy. This is normal and the breeder will perhaps keep the best as his “tategoi” whose colour will develop over time. Because the market demands bright colours, many breeders choose to place the rest of the harvest in concrete ponds and feed colour enhancing food to the koi to brighten them up. In the process, growth is sacrificed and hi will be finished early.  I have seen countless young fish that have returned to the light orange colour within a few weeks after they were released in the koi keeper’s pond. Unfortunately, the quicker the pigment cells are encouraged to develop, the quicker the decline after the state of finish has been achieved. Even koi keepers with exceptional skill will only succeed in delaying the decline for a while.

The hi colour (not the pattern), tends to develop from the head towards the tail. Early signs of the weakening of the hi can show in one of three ways, namely from the head, from the kiwa, or as a total weakening of the whole hi plate. All three are equally common, but the total weakening of the hi is startling and may turn an excellent fish into something worthless within a few weeks. Weakening of the hi around the kiwa, is more gradual and there may be indications that this may happen when inspecting a young koi. This is one of the reasons why such emphasis is placed on clear-cut kiwa by knowledgeable persons when selecting koi. Potential fading hi can be detected at or around the kiwa edge. The hi starts to weaken around the last scale, showing a little white or just lightening of the colour. The impression of “bleeding” hi at the kiwa may also indicate a future problem. If you see a koi in your collection where the red pattern on the head change, it is also time to be concerned but at least you can see this happening. If it is a koi you are thinking of buying you will mostly have no idea. If you inspect the koi carefully, you can often see pinkish markings where the hi use to be, or pink/red spots where the pigment is still a little stronger. The reason for the loss of hi should be distinguished from hi-kui which is a disease. Most type of degeneration of the hi is either through the genetic make up of the koi or through a trigger (poor conditions etc). On the whole the purple type hi is the least stable, with the more orange types being better at holding their colour, but all types and shades can break up. Some koi which are vulnerable to loosing their hi can have a trigger to start the failing, when conditions return to normal the recession is halted. It will however start to fade again with the first hiccup.

All the above should be remembered when considering a new koi. Look closely at the edges of the patterns and pick a koi with an even shade from head to tail and hope for the best. Just remember, the hi on both cheap koi and expensive koi can fail.

Sumi, whether it is on a Showa, Sanke, Utsuri or Bekko remains an enigma. Sumi is normally submerged in a young koi, and appears bluish. This submerged sumi may appear over time and become dark glossy black like printers ink. Some of these bluish markings will disappear completely. There are sometimes sumi that in young koi will be up and prominent. This sumi will either disappear or will become obscure and unattractive. As the koi develops, it is said the sumi will grow while hi will remain either the same or will stretch with the koi to a lesser extent. This makes the prediction of how sumi will develop very difficult. A general rule is that the earlier a sumi pattern is defined and finished, the poorer its quality will be. It may remain low quality sumi, it may break up into jari sumi or it may disappear. I have also witnessed that submerged sumi may be covered by the white (shiroji) if the latter colour is very strong and thick. When considering a young koi, submerged sumi is therefore preferred because it stands a better chance of becoming the ideal thick, glossy sumi that is preferred. Although it should be submerged, concentrate on those areas where it has partially surfaced. This should be of high quality. If one or two tejima stripes are noticeable in Bekko or Sanke, or Motoguro in Showa, it may be an indication of future quality. Sumi in the mouth of a Showa may also indicate strong sumi.

               hi_utsuri_08042010_before       hi_utsuri_after
               Photos: Neville Boardman

While hi develops from the head to the tail, the sumi develops from the tail towards the head. Weak sumi on the peduncle will therefore indicate weak colouration while strong sumi on the head/shoulder may indicate that the sumi may be strong. Genetics, water quality, feeding as well as temperature will influence the quality of the sumi over time. Water temperature has a marked effect on the quality of sheen and colour.  Both hi and sumi will become more intense, while the white becomes better finished. This will only benefit the appearance of the colour if the chromataphores are distributed on the surface of the skin, immediately under the scales or deep in the skin. If a fish don’t have this distribution of chromataphores, cooler water will not benefit the appearance of the fish to the same extent.

Sunlight does contribute to the health of koi, because it assists in the conversion of sterols in the skin into vitamins. It is also accepted that sunlight is important to finish koi with a healthy gloss. If you leave koi in the dark, you probably have noticed that it becomes a little paler at night. You may have also noticed, that young koi in an indoor fish tank without a full spectrum of lighting, will change from a reddish orange to a pale orange colour with silver washouts, but it will not turn completely white. Remember that the orange colour in the skin is not a tan, but cells containing pigment. It is not yet sure what long term effect the lack of decent light will have on a koi. Some people claim that too much sunlight may bleach the colours of a koi, or even cause sunburn. It is perhaps possible in shallow ponds in full sun, but sunlight loses its energy rapidly when passing through water. High energy ultra violet can only penetrate the water for a few centimetres. Direct sunlight may have an effect in overheating a pond.
Each Koi is born with a fixed number of chromataphores which remains relatively constant throughout its life. As the Koi ages and grows, these chromataphores, have to cover a larger area of skin therefore there is a tendency for the coloration to become paler (due to the chromataphores becoming less dense) or to fragment. This is why many stunning young Koi are not as attractive when they are slightly larger. Buying young fish from a known quality bloodline usually means you are buying fish with more dense chromataphores. This will result in the colour remaining even when the Koi has grown. In some varieties (e.g. Sanke and Showa) it is common for the pattern to change considerably as the fish grows due to the surface colour fragmenting and revealing a deeper different colour. When your koi turns white it means the chromataphores were destroyed and it cannot be reversed.

Chromataphores are branched cells, within which the colour pigment can be moved. The distribution of this pigment is affected by a number of different factors. Different water quality conditions can have a major impact on the coloration of the Koi. Raised levels of pollutants (e.g. ammonia, nitrite or nitrate) may cause the koi to lose its colour. pH and hardness affect coloration differently; red pigment tends to spread in softer, more acidic water, whereas black pigment spreads in harder more alkaline water and vice versa. Background colour may also influence the colour. Although it is difficult to merge into the background for a red and white koi, they do try to do so. Against a pale background the koi will contract the pigment to make them as pale as possible. The opposite occurs when the Koi is next to a dark background. This is one of the reasons why blue vats are used at koi shows to ensure the koi looks at its best. Salt is often added to Koi ponds as a treatment or to control nitrite toxicity, however, it causes the pigment to concentrate resulting in poorer coloration. It is said that long term exposure may cause this to become permanent. The same is true for antibiotics, whether added to the water or injected and malachite green based remedies.  
Koi which have lived in an algae rich, green pond often appear intensely coloured due to the colour pigment spreading in the chromataphores. At high summer temperatures pigments contract; at cool autumn and winter values they expand resulting in the koi looking at their best in the cooler months of the year. This list could be continued, but hopefully some of the examples my help to explain colour changes in your Koi which you have observed. Unfortunately these things don't happen in isolation, making it very difficult to ascertain exactly what caused the change in coloration of your koi.

Below is an example of a young imported koi that is rapidly losing its colouration. When purchased, the koi was an ideal example of deep orange-red. There was a suspicion that for a fish of 18 centimetres the colour was already nearing a finished state. The koi stayed in an fairly algae rich pond for four months with no apparent change in the  colouration but close scrutiny will reveal that scales around the dorsal fin and particularly near the lateral line was starting to fade around the edges of the scales. For various reasons the fish had to be removed from the pond and it was transported just a few kilometres and introduced to another pond.

Stability of colours

The changes witnessed here occurred in only three weeks. The water quality in the new pond was impeccable, the food remained the same but the companions in the new pond were mostly huge fish. The reason for this dramatic change will remain open for speculation, but the opinion is held that it is a genetic problem, exacerbated by early finishing of the colour, as well as the stress caused by the bewilderment of being placed in a confined space amongst the huge perceived “predators” around it.

The next example is a young Showa from a respected breeder in Japan. The fish was imported and photographed in June 2009. The second photo was taken in November 2009. The reasons for the dramatic change are unknown.

                          showa_june_2009         showa_23_november_2009


The same can happen to Goshiki.



                   goshiki_2       goshiki_lost_color_2

                   Photos: Romie Strydom

The unknowns

All the abovementioned, points to the fact that purchasing a young/small koi is really the same as throwing a dice.  Throw it and hope for the best. Although there are certain signs to consider, the buyer is really at a disadvantage. All the role-players in the supply chain know more that the buyer.

The facts a buyer may not know

  1. The genetic background of the parents.
  2. Mostly a buyer will not even be sure if the koi really comes from a stated breeder.
  3. The conditions in which the koi was reared.
  4. Water quality of rearing facilities.
  5. Food that was fed to the koi.
  6. Chemicals previously used.
  7. Netting process when dragged.
  8. Handling of the koi since it was netted from the mud pond.
  9. History of disease.
  10. Appearance of the colour plates a month ago.
  11. Amount of colour enhancers fed to the koi.
  12. The true age of the fish.
  13. Conditions of transport between breeder, agent, wholesaler, and retail outlet.
  14. Conditions of the quarantine facility.
  15. Was the fish quarantined at all?

Facts a seller may not know

  1. The genetic background of the parents.
  2. The conditions in which the koi was reared.
  3. Water quality of rearing facilities.
  4. Food that was fed to the koi.
  5. Chemicals previously used.
  6. Netting process when dragged.
  7. Handling of the koi since it was netted from the mud pond.
  8. History of disease.
  9. The true age of the fish.
  10. Conditions of transport between breeder, agent, wholesaler, and his own retail outlet.

Facts a breeder may not know

  1. The specific genes inherited from the parents.
  2. Conditions of transport between agent, wholesaler, and retail outlet.
  3. Conditions of the quarantine facility.


It is obvious why some koi keepers visit Japan to select their koi for show purposes. The fact remains that if there is no “rapport” between the buyer and the breeder, the list of “unknown factors” will only marginally get shorter.

Last Updated on Monday, 16 December 2013 13:43