Koi or Common Carp
Common carp are large, greenish-brown freshwater fish native to Asia and eastern Europe. They are the first known domesticated fish, farmed for food over 2,000 years ago in ancient Rome. Common carp have been successfully introduced all over the world for aquaculture, often causing serious environmental damage in their non-native habitats. They tolerate a wide range of water temperatures and conditions, and are omnivorous, eating algae, worms, plants, snails and small insects.
For centuries, common carp have also been bred into colorful, highly ornamental pond fish called koi. Koi are usually bred for very specific patterns and color combinations, usually including white, gold, orange, black or blue. When released back into the wild, koi populations usually revert back to their natural olive-green or brown color within a few generations. Common carp are hardy and grow quickly, up to four feet long. In the wild, common carp often live for 15 to 20 years. In captivity, koi regularly live for 50 to 70 years.