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.
- 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.
- 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.
- Dragon Eye goldfish have protruding eyes. As the names suggest, the Bubble Eye goldfish and the Telescope Eye goldfish both belong to this group.
- 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.