Related species

Goldfish have been bred from the crucian carp (Carassius auratus Gibel) in China, and remain the closest wild relative of the goldfish. [9] [10] Previously, some sources claimed the crucian carp (Carassius carassius), a wild version of the goldfish. However, they differ in many respects.C. auratus have a more pointed snout, while the mouth of a C. Carassius is well rounded. Gibel C. often has a gray / greenish color, and goldfish are still in gilded bronze. young carp have a black spot on the base of the tail, which disappears with age. In this place, C. auratus queue is never present. C. auratus have fewer than 31 scales along the lateral line, while goldfish have 33 or more scales. 
When in nature, the goldfish are olive green. Introduction of the wild goldfish can cause problems for native species. Goldfish can hybridize with other species of carp. In the three generations of breeding, the vast majority of goldfish breeding back to their natural color of the oil. The mutation that gave rise to the goldfish is also known from other cyprinid species such as common carp and tench. Koi may also interbreed with fish from goldfish to produce a sterile hybrid. 
There are many varieties of goldfish home. Fancy goldfish are unlikely to survive in the wild because of their bright fin, but the most resistant varieties Shubunkin can survive long enough to breed with wild relatives. Common goldfish and comet can survive and even thrive in any climate that supports a pond.