Koi fish are a colorful, ornamental versions of the common carp. Though carp domestication is believed to have begun in China as far back as the 4th century, modern Japanese koi are believed to date back to early 19th-century Japan where wild, colorful carp were caught, kept and bred by rice farmers. There are now dozens of different color varieties of koi.

Koi can grow up to 3 feet (90 centimeter) in length.

Wild koi are native to the fresh bodies of water around the Black, Caspian and Aral Seas. Domesticated in the 19th century, carp have now been introduced throughout the world.

Koi have an average lifespan of 40 years. It is believed that the oldest-known koi lived to be nearly 230 years old; the age was determined by testing the fish's scales, which produce growth rings much like a tree.

Koi are omnivorous feeders who will eat food found at all depths of water.

The Japanese koi at the Kids' Farm are fed a floating pellet, though they will also eat aquatic insects, algae and plants.

Koi will migrate significant distances to reach their preferred spawning grounds — flooded meadows and stagnant marshy areas. The breeding season is in the spring, around May or June. Females reproduce for the first time when they are between 4 and 6 years old, males when they are between 3 and 5 years old.

Once they reach sexual maturity, they will breed every year. They attach their sticky eggs to water plants or any object submerged in the water. The young hatch as larvae and stay in warm, shallow flooded areas until they are large enough to brave more open waterways.

Koi have been introduced all over the world, and they are farm-raised in large numbers for food, for ornamentation and for sport fishing. Wild populations are now at risk from hybridization with released or introduced domestic stock. They are also threatened by river control — wild carp need flooded areas in order to reproduce.