All Goldfish variations belong to the same species, Carassius auratus auratus. According to Chinese tradition the different Goldfish variations are divided into four basic groups.

1. Ce goldfish or Grass goldfish are goldfish without any “fancy“ features. The Common goldfish is very similar to the carp from which it has been bred; the main distinguishing feature is the colour modification. Unlike the wild carp, the Common goldfish can be obtained in a wide range of colour variations, including white, black, lemon yellow, orange and of course the golden colour.
2. Wen goldfish are goldfish equipped with a dorsal fin and a fancy tail. An example of a Wen goldfish is the Fantail goldfish that has a dual-lobed tail that can reach a size of three inches.
3. Dragon Eye goldfish have protruding eyes. As the names suggest, the Bubble Eye goldfish and the Telescope Eye goldfish both belong to this group.
4. Egg goldfish is a goldfish that has no dorsal fin. One example of Egg goldfish is the Japanese Ranchu goldfish. If a Bubble Eye goldfish is without dorsal fin, it is considered a part of this group instead of the Dragon Eye goldfish group.