The ranchu is a hooded variety of fancy goldfish developed in Japan. It is referred to as the "king of goldfish" by the JapaneseThe modern-day ranchu is a Japanese development of the lionhead. They are the direct outcome of crossbreeding experiments of different Chinese lionhead specimens.
The ranchu is a highly regarded fancy goldfish in Japan. Compared to lionheads, ranchus have a more downturned tail and tail fin.Although similar to lionheads, ranchus have more-arched backs and have much shorter tails that are tucked-in at a sharp angle.
A ranchu has an egg-shaped body with a deep belly that is between 5/8 to 3/4 the length of the fish. This goldfish does not have a dorsal fin and breeding standards require that the back should not have any vestiges of the dorsal fin on it. The back should be rounded and not flat, as in the case of lionheads. The area of the caudal peduncle should curve sharply downwards to meet the tail. The caudal peduncle itself should be broad and neither lengthy or too short (a properly formed caudal peduncle avoids swimming motion impairments to this type of goldfish). The ranchu's tail meets the caudal peduncle at a forty-five degree angle, giving the fish a unique swimming motion. Furthermore, the tail lobes are rounded, and all other finnage are paired.