This fish is the common/basic Chinese twintail goldfish; it doesn't have an English name and in UK is usually sold as the fantail, which it is not. The Chinese name, man-yu, simply means graceful fish.
The man-yu is intermediate in form between the fantail (short, rounded finnage, well forked tail) and the veiltail (long, pointed finnage, minimally forked tail); the ryukin is another intermediate form and has a dorsal hump, and is quite distinct from this fish which has a smooth dorsal contour like the fantail/veiltail. Calico colouration can be superb, with a full range of vibrant colours, and a careful outcross to good specimens should improve the calico colouration of fantails or veiltails, which can be a bit dull in colour by comparison.
In fact, there is a continuum of form from the veiltail through the fantail and the man-yu to the ryukin, these varieties differing in the length-vs-depth of the body, the length of the finnage and the carriage of the tail.
When you go shopping for a basic, twintailed goldfish in a pet shop or most other aquatic outlets, this fish is what you are buying, imported from the Far East. For fantails or veiltails you need to visit a specialist outlet or join a goldfish club.
There is no British standard for the man-yu and there is unlikely to be one because this is not a variety that is competed in goldfish shows.
It has a short, fairly deep, fantail-style body with a divided caudal and anal fin. Finnage is usually medium to long and well rounded, with a deeply forked tail.
Colouration is metallic or, more usually, calico.
These are Chinese fish photographed in Honk Kong in July 2006. Some of the patterns now available are striking, such as the red-on-silver scales (top fish), the red band in a white tail (in both sets of pictures) and the silver-white collar on a red fish (bottom set).
Calico oriental twintail shown at BAS 2008. Notice the forked tail and the shorter, rounder paired fins compared with the veiltail. Ideally such calico fish would have some background pale blue colouration and more red than orange colour. Notice also the nice deep body contour.
Calico fish with rich colouration. Photographed in Hong Kong, December 2000.
Blurred portrayal of a shoal of Chinese twintails (man-yu). Hong Kong, December 2000.
© Bristol Aquarists' Society