Shubunkins are similar to the common goldfish and comet goldfish in appearance. They were first bred in Japan, from crossbreeding the calico telescope eye goldfish (Demekins), comet goldfish, and the common goldfish c. 1900. They have streamlined bodies with well-developed and even fins. However, the Shubunkins are calico goldfish; they possess nacreous scales (an intermediate between metallic and transparent scales that are pearly in appearance). The overlapping patches of red, white, blue, grey and black (along with dark speckles) normally extend to the finnage of Shubunkins. Blue is the most prized colour in Shubunkins. Calico originally denoted three coloured varieties of goldfish that did not include blue. The best blues are produced from line breeding of good blue specimens of Shubunkins. Sometimes good blues may be obtained by breeding bronze (metallic) with "pink" (matte-scaled) goldfish, but a grey slate colour may result instead.
It may take several months for the nacreous coloration to develop on a young fry (baby fish). Shubunkins are excellent pond fish because they reach a length of 9 to 18 inches (23 to 46 cm) at adulthood. A Shubunkin goldfish is considered an adult at 1 to 2 years of age, even though they live much longer. wikipedea