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 ...

For example, stress can temporarily make your betta fish look duller. Luckily, you can restore their colors by providing a well-maintained aquarium and a proper diet. Koi fish, like most fish on ...

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 ...