--- title: "Koi (Cyprinus rubrofuscus) | AnimalTracks.wiki" description: "A pet carp bred into over 100 colour varieties that, in one study, sought out a human hand." image: "https://animaltracks.wiki/images/animals/koi-1.webp" published: "2026-10-10" updated: "2026-10-11" --- # Koi (*Cyprinus rubrofuscus*) > **Status**: Checked against 5 sources, listed under Sources below. > **Tagline**: A pet carp bred into over 100 colour varieties that, in one study, sought out a human hand. > **Soundtrack Vibe**: Neo-Classical & Baroque Chamber // Clara Schumann, "Variations on a Theme by Robert Schumann, Op. 20" > **Soundtrack Links**: [Spotify](https://open.spotify.com/track/0CHNLju7fsYFDHt1XQytEv) > **Vibe Match**: Koi are all carp, bred from odd colour variations into over 100 varieties in red, white, black, yellow, brown, gray and green. Clara Schumann's Op. 20 does it to a melody: one theme, then seven variations that keep its shape and change its colour. ## Biological Superpowers & Stats - **Taxonomy**: *Cyprinus rubrofuscus* - **Danger Level**: Low - **Conservation Status**: Least Concern ([IUCN Red List](https://doi.org/10.2305/iucn.uk.2022-1.rlts.t166052a159637283.en)) - **Superpower**: In one study, sought out a human hand for touch even after a full meal - **Habitat**: Outdoor ponds and water gardens; the wild species lives in Laos, Viet Nam and China - **Diet**: Mostly plant foods such as rice and corn, plus live shrimp and their own young - **Tags**: fish, freshwater, omnivore, domestic-pet, colorful ## Natural History & Behavior ## Pets That Poison Their Own Pond Koi are ornamental varieties of domesticated common carp, first bred in Japan. Their own waste can kill them. > **Self-poisoning fish** > Without a good filtration system in their pond, koi would poison themselves, as they excrete ammonia. Keepers put them in outdoor ponds with very clean, oxygenated water and plenty of shade. The shade matters: koi can get sunburned. ## A Rice-Paddy Fish Turned Rainbow Chinese farmers raised carp in rice paddies for food in the 1600s, and the practice spread to Japan. There, people spotted odd colors in some of the carp and bred them. Today there are over 100 koi varieties, in red, white, black, yellow, brown, gray and green, and many combinations of those. Koi eat mostly plants, with rice and corn among their favorite foods. They will also eat live shrimp and even their own young, called fry, before the little fish's colors come in. ## How Big, How Old, and Which Carp Sources name koi two ways. The San Diego Zoo files them under *Cyprinus carpio*, the common carp. A 2021 study names them *Cyprinus rubrofuscus*, which FishBase and the Red List treat as a wild species. Each figure below says which fish it belongs to. For koi, the zoo gives a maximum length of about 3 feet (91 centimeters) and an average weight of about 35 pounds (16 kilograms). It says koi typically live 25 to 35 years if cared for properly. For the common carp, AnAge lists a maximum longevity of 47 years in captivity. For the wild *Cyprinus rubrofuscus*, FishBase lists a maximum length of 28 centimeters (standard length) and places the species in Asia: Laos, Viet Nam and China, from the Amur to Red River drainages. Koi, by contrast, are kept as pets on 6 out of 7 continents, the zoo says. The Red List rates the wild species Least Concern, assessed in 2020, and the zoo says koi are not endangered. ## Fish That Seek Out a Hand In a study published in 2021, at an aquaponics learning center in Brooklyn, a researcher offered a submerged hand to seven adult koi, each between 40 and 60 centimeters long, without forcing contact. The koi spent more time than expected within reach of the researcher, and they started the touching themselves by mouthing, brushing and bumping the hand. Some did this often and others rarely. The koi stayed interested even after being fed to satiation (full), which the authors say suggests the interest may not be about food. The zoo adds that koi can be taught to eat from a person's hand. ## Frequently Asked Questions ### How long do koi live? Usually 25 to 35 years with good care, according to the San Diego Zoo. *(Source: [San Diego Zoo Wildlife Alliance]())* ### Are koi an endangered species? The Red List rates Cyprinus rubrofuscus, the wild carp of Laos, Viet Nam and China whose name one koi study uses, as Least Concern, assessed on 20 March 2020. That rating describes the wild fish, not the pond varieties. *(Source: [FishBase]())* ### Do koi like being touched? In one study of seven adult koi at a Brooklyn aquaponics center, the fish chose to stay near a researcher's submerged hand and touched it of their own accord. How often they did so varied a lot from fish to fish. *(Source: [Fife-Cook & Franks 2021]())* ## Sources 1. [Bogutskaya & Huckstorf (2022). Cyprinus rubrofuscus. The IUCN Red List of Threatened Species 2022: e.T166052A159637283.]() 2. [Fife-Cook & Franks (2021). Koi (Cyprinus rubrofuscus) Seek Out Tactile Interaction with Humans: General Patterns and Individual Differences. Animals.]() 3. [Koi (Cyprinus carpio). San Diego Zoo Wildlife Alliance.]() 4. [Cyprinus rubrofuscus Lacepède, 1803. FishBase.]() 5. [AnAge entry for Cyprinus carpio. AnAge: The Animal Ageing and Longevity Database, Build 15, Human Ageing Genomic Resources.]() *Published October 10, 2026. 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