Despite their amazing popularity worldwide, Koi, which are domesticated Common Carp, were unknown outside of Japan until the early 1900’s. Today a huge array of colors and scale/fin types, some of which command astronomical prices, are featured in the trade and at highly-competitive shows. Living to at least age 50, and reputedly for much longer, Koi can top 3 feet in length and are best kept in outdoor ponds.