Carassius auratus is native to Asia and was introduced to Australia in 1876 as an aquarium fish. Since its release into the wild, it has spread into the streams, ponds and dams of the southern half of Australia - extending into south-east and south-west Queensland and the Fitzroy and Burnett catchments. It is considered a potential pest.

Adult Goldfish are typically about 20 cm in length. The largest Carassius auratus on record is 48 cm. Aquarium fish are brightly coloured - from silvery white to golden yellow, red, brown and black. Some are spotted or mottled. Once released into the wild, the bright colours are usually lost within a generation or two and the fish become a drab bronze or olive-green colour. They are sometimes mistaken for carp, but carp have whiskers on the corners of their upper lip and goldfish don't.

Goldfish are a subtropical, freshwater fish, but they prefer cooler waters. They can survive in still water and can tolerate relatively high temperatures and low oxygen levels. Their diet includes plants, small crustaceans and aquatic insects.

Spawning season is in Spring and Summer. Male goldfish chase after females, nudging her so that she will release her eggs so he can then fertilise them. The eggs are sticky and adhere to aquatic plants and other underwater objects. A large female goldfish can lay several hundred eggs at a time. The eggs hatch in about a week. Goldfish become sexually mature at three to four years of age, but they need enough water and the right nutrition for this to happen. They usually live for about ten years, but some have been known to live for thirty.