A koi's color cells sit at different depths in the skin, some right near the surface and some deeper in, which ultimately determines how bright the fish appears. The brighter the fish, the bigger ...

Koi fish are what you might call a happy accident. In the 1600s, Japanese carp farmers began noticing unusual color variations among the fish. "The popular koi fish of today are actually ...

Among the most difficult to save are those that live in water. David and Jane Pierce have owned — and loved — these koi fish for 25 years.Credit...Stella Kalinina for The New York Times ...

These polychromatic swimmers are definitely deserving of admiration. Koi fish have got a lot going for them. "[They are] not only a pet, but also art," says Taro Kodama, president of Kodama Koi Farm. ...