Koi selection methods from back in the day: choose based on body shape and color
Koi selection regarding body shape and color: the fish's back should be straight, the body balanced left and right, the swimming posture steady and upright, and the body robust and powerful. The shape of the cheeks and the position of the mouth should be well-proportioned, without crookedness, full at both ends and not sunken, and all fins should be symmetrical and complete, moving flexibly when swimming....
When selecting Kohaku (red and white koi), first pick those with large markings on the head. First, on the head of the small fry you must see the edge of the red patch, with white showing at the mouth, or a broken marking behind the mouth; this must be very clear. If you can see that kind of red patch, it will have future potential. The red patch should not cover the eyes; both eyes must be visible, just as if the red patch were placed on top of the head. This can be seen very clearly at the fry stage, and the red must have depth. Those with loose head markings lacking individuality can be culled. Next is having a shoulder break, meaning the red patch behind the skull must be split, even if only by a very small, fine break; otherwise it will not be the makings of a high-quality fish.
In choosing parent fish, color quality and pattern are the priority considerations, and when comparing color quality with pattern, color quality should be given even higher priority; it is best to choose large fish of 80-90 cm.
When judging the quality of small fish of 3-10 cm, it is generally rather difficult; if they are over 15 cm, it becomes somewhat easier. Specifically, for varieties with red markings, in fry of 3-10 cm the red patches are not very obvious, and some may even show color bleeding. In poor-quality fish, the red patches on the body will still change and may fade; this happens especially with the red patches on the rear half, which often disappear after growing to a certain size, leaving a white base and turning the fish into an inferior one. Small fish with blurred, unclear red patches are of poor quality; no matter how large they grow, they should not be kept for further rearing and should be culled in good time.
For fish from the same spawn raised under the same conditions, deeper color is better than lighter color.
For tosai (yearling koi), it is harder to distinguish and judge the quality, but you must look at the glossiness of the red patches; red patches with this silky, bright color quality do not fade easily and are of high quality; those with a rough surface, uneven color, and no certain depth also fade easily, and fish of this quality should be culled.
When selecting Kohaku (red and white koi), first pick those with large markings on the head. First, on the head of the small fry you must see the edge of the red patch, with white showing at the mouth, or a broken marking behind the mouth; this must be very clear. If you can see that kind of red patch, it will have future potential. The red patch should not cover the eyes; both eyes must be visible, just as if the red patch were placed on top of the head. This can be seen very clearly at the fry stage, and the red must have depth. Those with loose head markings lacking individuality can be culled. Next is having a shoulder break, meaning the red patch behind the skull must be split, even if only by a very small, fine break; otherwise it will not be the makings of a high-quality fish.