Choosing Koi With A Future


When buying a koi carp of any size, it is important to look for a decent body and head shape that are in proportion with each other. However, a fat koi isn’t necessarily a koi with good shape, there is a little more to it than that.

It is also important to bear in mind that koi don’t usually have good ‘volume’ at a small size, and that a koi will build its frame (bone structure) as it grows. Hence, buying a small koi will always be a little more difficult than buying a bigger two or three-year-old.

To help you understand body shape we have split it into several areas, all of which have equal bearing on the size potential of the koi and how impressive it will be when it is bigger.

Never choose a fish primarily for its pattern. This can only lead to long-term disappointment


headStudying a koi’s head and understanding what constitutes a good shape is made easier by comparing it to the other fish in the bowl. A good head will be broad and long, with a wide mouth, and the eyes set a good distance apart and not close to the mouth.

It is quite common in the UK to see koi that have a narrow or short head, with the eyes being too close to the mouth. Such koi will seldom get big and should be avoided. Another aspect to look for is the underside of the cheeks of the koi. The profile of the cheekbone should be free of defects. Also make sure that the gill covers follow the same smooth line as the overall head shape, and don’t stand proud, bulge or flare outwards just before the body.


Jitai means ‘height’ and quite literally refers to the height of the body of the fish. Don’t be fooled that a hump behind the head is a good thing, as this isn’t Jitai and has no bearing on size. Jitai is the height of the body of the koi between the back of the head and the highest point of the body. A good strong curve up over the back of the koi is a good attribute and a key factor in determining size potential, as well as helping determine the kind of body shape the koi will develop.

Also, when looking at Jitai, you will often see that it is prominent in such a way that it looks as if the koi will be able put on more weight in the shoulder area. This can help you understand the way the shape will develop. One thing that you should remember is that good Jitai is important, but it is still possible to have a koi that has too much height, which will make the fish look short in relation to its build. However, Jitai is often less prominent in koi descendant of ‘magoi’ blood, soo bear in mind the background of the fish in question.


termsOzutsu is the tail joint , which should be thick and strong. However, in very small koi the tail joint will tend to blend subtly in to the tail, making it somewhat harder to assess. In larger koi it is better to look for a thicker Ozutsu. Another factor that needs to be watched is the depth of the tail joint, as a shallow tail joint can often make a female koi look overly female as it grows, and will also make the tail pipe look too thin. Carefully choosing a koi that has good Ozutsu can help you obtain a koi that will keep a good, strong but trim body as it approaches jumbo size.

Other points to consider

Fins should be in keeping with the size of the fish, and large pectoral fins are considered desirable, as opposed to small ones. Large pectoral fins don’t mean that the koi is male, and sexing koi from pectoral fin size is extremely inaccurate, particularly in small koi. Be certain that the pectoral fins don’t have a twist (or curl), up or downwards towards the tips. Make sure that the tail is straight where it enters the body, and that it doesn’t point off at an angle. The bodyline of the koi must be straight, and the head must also be straight where it joins the body.

Carefully choosing a koi that has good Ozutsu can help you obtain a koi that will keep a good, strong but trim body as it approaches jumbo size.


Never choose a fish primarily for its pattern. This can only lead to long-term disappointment. You should always choose quality first. A fish with good pattern, but low quality, will please you only temporarily, and in time you will ultimately lose interest, particularly when you notice no improvement in quality over the coming years.


However, by choosing a koi for its quality, you may not particularly like the pattern at first, but in time you will come to admire it as it grows and blossoms in your pond. How many big koi have you looked at in awe, that you wouldn’t have liked the pattern on if the koi was small? Consider also that some patterns will suit a small koi very well, whereas others are what I would call a ‘big fish pattern’. A flowery pattern with large amounts of white can look beautiful on a small koi, but as the koi gets big, it can start to look somewhat bare.

A ‘big fish’ pattern can often be heavy and perhaps a little bland, but can look much better as the koi gets big. Why?

Take a look at the pattern of a kohaku for example, and observe how far down the side of the koi the pattern falls. Let’s assume that we have an imaginary kohaku with a continuous hi pattern (not particularly desirable) but this pattern falls relatively deeply (in places) down the side if the fish. Throughout the length of the fish, the pattern is crossing above and below the lateral line numerous times. In a small (20 cm) fish, this would hold little interest to most people, as it would appear to have no pattern, just a continuous hi.

But, what happens when the koi grows up? Well, the pattern will obviously grow with the koi, but the koi will also gain weight considerably with size. What will inevitably happen, is that where the koi would have been relatively ‘flat sided’ in appearance as a small fish, it will put on weight and the body will become much thicker and tubular in profile. Because of this, any areas of pattern that fall above the lateral line will appear shallower with the areas of white ground becoming more apparent as the pattern is seemingly ‘pushed upwards’. Any pattern falling below the lateral line will appear to wrap towards the underside of the koi.

The overall effect would be that the same pattern seen on our imaginary small koi, would look considerably more interesting on our big koi. Remember that in two high-class koi of exactly the same quality, pattern can make one fish ten times the price of another. The main point to our ‘imaginary koi’ is not to convince you to rush out and buy a koi with a bland pattern, but to emphasise how a heavier pattern will often suit a big koi better than a small one. It is often the pattern that pushes the price of a koi beyond people’s reach.

Sumi quality

Sumi quality is all too often overlooked. It is incredibly easy to buy a koi such as a Showa that looks like a fantastic prospect for the future, with an abundance of underlying sumi. However, there is more to sumi than meets the eye, and all too often the underlying sumi will never develop.

Several different types of sumi exist, so we will keep this section as simple as possible. Two main words are used for describing sumi. One is ‘Honzumi’, which is a very high quality glossy black, and the other is ‘Nabesumi’, which is low quality and dull.

When looking at the sumi, it is important to be able to see at least one scale of good sumi in order to assess the likelihood of future sumi developing. Assuming that the koi does have one scale with decent sumi, it should be very ‘black’, shiny and ideally darker towards the centre of the scale. In many cases, the outside edge of the scale will be darker than the centre (looking like a reticulation of sumi), which is an indication that the sumi isn’t as good. Such sumi will often fade if the koi is subjected to stressful situations, like being viewed in a bowl for a minute or two.

In the case of ‘Kage’ sumi, the sumi that starts from the centre of the scale is the type that will develop well, whereas the type that starts as a reticulation will often stay as ‘Kage’.

There is more to sumi than meets the eye, and all to often the underlying sumi will never develop.

Beware of koi that only have sumi showing on top of the red pattern, and in such cases, pay particular attention to the quality of even the slightest bit of sumi that is showing on white ground – completely disregard how good the sumi looks where it falls on top of the hi pattern.

When choosing Shiro Utsuri, one helpful tip is to bowl any koi that you are interested in and wait for a few minutes. Observe the koi where the sumi fades while in the bowl, and reject them regardless of pattern. Choose from the ones that don’t fade during the stress of being in the bowl.

When looking for Motoguro (sumi in the base of the pectoral fins), pay careful attention. A completely black pectoral fin has a chance of staying completely black, but if the front ray of the pectoral fin is white, there is a much higher likelihood of the sumi receding later on to become beautiful Motoguro. Motoguro can also develop from seemingly nowhere. If the fin are white, take a look at the very base of the fin, or even the ball of the pectoral joint. If there is even the slightest trace of sumi there, then there is hope.


Your dealer should ask you about your pond before selling you a koi. It is important for yu and your dealer’s reputation that you buy a koi suited to your pond, and keeping knowledge. There is no point in selling a high class koi with jumbo potential to a small, shallow, or unheated pond. You should also bear in mind that if you want to grow female koi you will need a deep pond and, more importantly, better water than a pond for keeping males. Don’t waste your money on an expensive high class koi with great potential if your keeping skills and pond will prevent you from impressing yourself with your long term results.

Unfortunately, people in this country generally can’t grow fish fast enough to learn from them. Try to learn about the benefits of soft water and other techniques that will help you grow your koi.


The intension of this article, and also ‘part one’, is to help you find koi that you will enjoy keeping and growing greatly for many years. However, it is important to keep things in perspective. You get what you pay for, and become very fussy after reading this article, then the chances are that you won’t be able to find a koi that will meet your requirements.

Cheap koi are always cheap for a reason. It may be because of a fault of some form, or perhaps the koi from small parents and has been produced for the ‘export’ market, or perhaps simply because the breeder knows that the koi doesn’t have a great future. The most important thing of all to remember when buying a koi, is to ask about the parents. Try to be analytical but realistic when looking for your next koi – look for an overall decent package of attributes.