How Koi keeping started
Japanese rice farmers kept carp in a designated pond and would grow them into fingerlings during the summer. In the fall, they would harvest the carp and then they dry/salt them. During the wintertime, the farmers would eat the carp for a source of protein.
Some of the carp had spots of red color. The farmers took note of this and crossbred the carp with the color mutations. After years of trial and error, the first color bloodlines were established. The Kohaku variety is believed to be the first modern type of Koi to appear.
At the beginning of the 20th century, german carp (doitsugoi) were brought to Japan. The Koi breeders established new bloodlines with the scaless carp from Europe. The Shusui Koi variety is the most popular doitsugoi today.
Up until the 1960's, Koi were almost exclusively kept in Japan. With the advent of jet travel and polyethylene bags, the art of keeping Koi spread around the world.