Common in ponds and aquariums, goldfish have been bred and kept as pets for some 1,000 years. The Chinese were the first people to breed the fish, creating ornamental varieties from the original dull, greenish-brown fish. Centuries of breeding have created more than 125 types of goldfish, many with unusual characteristics. The type most commonly found in pet shops is called the comet. The scientific name of the goldfish is Carassius auratus.Although native to East Asia, goldfish are now common throughout the world. They are best known as a popular indoor pet, but they also live in outdoor freshwater bodies such as rivers and lakes. Goldfish are hardy and can thrive in cold water.Goldfish will usually grow to a size suitable for their environment. Thus, while small aquarium goldfish are only 2–4 inches (5–10 centimeters) in length, goldfish living in bigger spaces can be 6–14 inches (15–36 centimeters) long. Some goldfish have even reached 2 feet (0.6 meter) in length.Goldfish resemble other members of the carp family, but variations in appearance are common. Like carp, they are naturally greenish-brown, but they may also be gold, red, orange, white, black, or a combination of colors. Goldfish also differ from carp in that they do not have whiskerlike barbels (feelers) dangling from their upper lip. One unusual breed of goldfish is the celestial, which has eyes that jut out and always look upward. Another is the lionhead, with a curious growth on its head that is said to look like a lion's mane.Goldfish eat a variety of foods, including plants, algae, insects, and small crustaceans. Wild goldfish sometimes swim together in schools. Although goldfish are usually not aggressive, they can become possessive of their territory in an aquarium.Most goldfish are ready to reproduce by their second year. Breeding can happen at any time in indoor aquariums. Outdoor fish breed during spring or summer. As the time for breeding approaches, females get a rounder belly and males may get small bumps on the head, back, and fins. Goldfish can produce thousands of eggs during each breeding season. The eggs usually hatch in less than a week. In proper conditions, a goldfish has an average life span of 7–10 years. Some live to the age of 25.
Although many pet goldfish come in a small bowl, it is better for their health to move them to a larger container. Goldfish can be fed dried flake or pellet food, but owners should also give them some food that they would eat in the wild. Goldfish tanks are rather hard to keep clean because goldfish produce a lot of waste. The water should be changed regularly. Putting small pebbles on the bottom of goldfish aquariums helps to create a home that looks like a pond. Aquariums should also contain live plants on which goldfish can munch.
