Crucian carp,Goldfish

The goldfish (Carassius auratus) is a freshwater fish in the family Cyprinidae of order Cypriniformes. It is commonly kept as a pet in indoor aquariums, and is one of the most popular aquarium fish. Goldfish released into the wild have become an invasive pest in parts of North America.

Native to East Asia, the goldfish is a relatively small member of the carp family (which also includes the Prussian carp and the crucian carp). It was first selectively bred for color in imperial China more than 1,000 years ago, and several distinct breeds have since been developed. Goldfish breeds vary greatly in size, body shape, fin configuration, and coloration (various combinations of white, yellow, orange, red, brown, and black are known).

Chinese tradition classifies goldfish into four main types. These classifications are not commonly used in the West.

• Crucian (also called “grass”) — Goldfish without fancy anatomical features, similar to Crucian carp or grass carp except for their coloration. These include the common goldfish, comet goldfish and Shubunkin.
• Wen — Goldfish having a fancy tail, e.g., Fantails and Veiltails (“Wen” is also the name of the characteristic headgrowth on such strains as Oranda and Lionhead)
• Dragon Eye — Goldfish having extended eyes, e.g., Black Moor, Bubble Eye, and Telescope Eye
• Egg — Goldfish having no dorsal fin, usually with an ‘egg-shaped’ body, e.g., Lionhead (note that a Bubble Eye without a dorsal fin belongs to this group.