Kohaku, a member of the Gosanke family, are koi with a solid white (shiro) body, and red (hi) patterns over top of the white. Kohaku are believed to be one of the first koi variety ever developed. Red fish first began to appear in Japan between 1804 and 1829, when a black carp with red cheeks was found. The white offspring of this black carp were bred with a Higoi (solid red fish), and the resulting offspring had red stomachs. Around 1829, a koi with red gill plates had been produced, and many more Kohaku-like varieties appeared over the next few decades.
Around 1888, a red-headed female carp was bred with a cherry-blossom-patterned male, and the resulting offspring became known as the Gosuke bloodline. The Gosuke bloodline is extinct today, but it is believed that all known bloodlines of Kohaku can be traced back to the Gosuke bloodline.
What To Look For
The solid white (shiro) of the Kohaku body should be unblemished, with a snowy or milky white color. A yellowish tint to the shiro is undesirable. The red (hi) should be brightly colored, with the same hue and shade across the entire body. The hi pattern should be balanced and evenly distributed across the body of the koi, but not necessarily symmetrical. Ideally, the hi markings should not spread down past the lateral line, and should not appear on the tail or fins.
The edges of the hi pattern (where the red meets the white) should be very clear and well-defined, with no shiro appearing in the middle of the hi patterns.