The koi is a cultivated form of which fish?

The Nishikigoi, also known simply as Koi, is a cultivated variety of carp (Cyprinus carpio). Koi, or -goi in compound forms, is the Japanese word for carp in general.

There are cultivated varieties of Koi that resemble the mirror carp or linear carp bred in Europe in their scale pattern.

The origin of Koi is not definitively established. It is possible that solid-colored carp originated in Iran and were brought to East Asia around 2000 years ago, where they were kept as insectivores and food fish. Since around 1870, Koi have been kept as status symbols by the nobility in Japan. Koi breeding has since become very popular in Europe as well.

Koi have a lifespan of up to 60 years and can reach a weight of up to 24 kg and a length of up to one meter. They lay approximately 400,000 to 500,000 eggs, and a young fish hatches from each egg in about four days. Koi feed on plants, insects, and worms. If the water temperature drops below 10°C (50°F), koi reduce their metabolism and enter a state of winter dormancy at the bottom of their body of water.

In Austria, keeping koi permanently in aquariums is prohibited.

Releasing koi into the wild, for example in ponds, poses a threat to native ecosystems: Native species are sometimes displaced, or diseases are spread. In Australia, for instance, there are increasing reports of anglers encountering sometimes very large koi, which is becoming a threat to local ecosystems.