RYUKIN (carassius Auratus)

The beautiful Ryukin Goldfish are a Japanese version of the Fantail Goldfish. They were developed from the common Fantail Goldfish. Like their Fantail counterpart, they are one of the more rounded or egg-shaped fancy goldfish.

The Ryukin Goldfish are easily differentiated from the Fantail by their extremely high back, which is often described as a dorsal hump. The hump starts in the neck region and gives a more pointed appearance to the Ryukin's head, They also have a wider caudal fin than the Fantail. A distinguishing feature common to both the Fantail and the Ryukin Goldfish is their split or double caudal (tail) fin.

Both Fantail Goldfish and Ryukin Goldfish are recommended for the beginner, but like all the goldfish with this rounded body shape, they can be susceptible to swim bladder problems. Other good beginner fancy goldfish are Common Goldfish, Comet Goldfish, the Shubunkin, and the Black Moor

http://animal-world.com/encyclo/fresh/goldfish/RyukinGoldfish.php