The most common fault on a Shusui is a messy shoulder scale pattern that lacks symmetry. Rogue scales can appear elsewhere on the body, further devaluing the Koi. Be wary, for in hard water, the mirror scales can turn grayish or black, and once this happens they never revert back to blue. As with Asagi, a clear head is essential for Shusui. Rather than the snowy-white preferred on Sub classification is determined by the pattern of the red and blue Asagi on the body of the Koi. Hi Shusui fashions hi that extends up over the back, so that the two contrasting colors are the red of the hi and dark blue of the mirror scales. These are unsubtle and quite striking Koi. Hana Shusui (Hana meaning flower in Japanese) also have more red than normal, but here it is in the form of an extra band between the lateral line and dorsal fin, with a break in between. In the best examples, the hi is laid out in a wavy pattern to give a flowery effect.
In Ki Shusui, yellow replaces the red. And yet another rare, Shusui-like Koi is the Midorigoi, which is greenish yellow with mirror scales. This one is benched in Kawarimono.
Shusui, means "autumn water" in Japanese. At first sight, these mirror-scaled Koi seem to have little in common with Asagi, but Shusui are actually the product of crossing Asagi with a German mirror carp in 1910 by Yoshigoro Akiyama, resulting in the very first Doitsu scaled Koi breed.
What to look for in Shusui
The color distribution is essentially the same as in the Asagi, but because there are no normal scales to give an overall reticulated effect, the smooth, sky-blue back is instead highlighted by the Doitsu scalation. In good examples, these armored scales form a regular pattern on the shoulders of the Koi and then run in two lines on either side of the dorsal fin, returning to a single line towards the tail. Another line is usually present along each flank, roughly following the lateral line.
Gosanke varieties, Shusui skin is more of an icy-blue, but should still remain free of blemishes.