In the late 1800's German koi were imported in Japan for food and crossbred with Japanese Koi. The Germans (Doitsu) selectively bred carp to have few or no scales to aid in the processing. During the Meija Erra (1868-1912) the Japanese bred some of their colored koi to two varieties of German carp which nearly doubled the varieties.

Doitsu Koi with lines of scales on the back and along the lateral lines are called "Kagami-goi (mirror carp)," and those without scales or with only one line of scales on each side along the base of the dorsal fin, "Kawas-goi (leather carp?)." There is a Doitsu version of almost every variety; Doitsu Kohaku, Doitsu Sanke, Doitsu Yamato Nishiki, and Doitsu Hariwake just to name a few. Doitsu Koi are to be viewed for the orderliness of scale arrangement and the absence of unnecessary scales. Each Koi should have the features characteristic of its own original variety.