Carp are a large group of fish originally found in Central Europe and Asia. Various carp species were originally domesticated in East Asia, where they were used as food fish. The ability of carp to survive and adapt to many climates and water conditions allowed the domesticated species to be propagated to many new locations, including Japan. Natural color mutations of these carp would have occurred across all populations. Carp were first bred for color mutations in China more than a thousand years ago, where selective breeding of the Prussian carp (Carassius gibelio) led to the development of the goldfish.
The common carp was aquacultured as a food fish at least as far back as the fifth century BC in China, and in the Roman Empire during the spread of Christianity in Europe.Common carp were bred for color in Japan in the 1820s, initially in the town of Ojiya in the Niigata prefecture on the northeastern coast of Honshu island. By the 20th century, a number of color patterns had been established, most notably the red-and-white Kohaku. The outside world was not aware of the development of color variations in koi until 1914, when the Niigata koi were exhibited in the annual exposition in Tokyo. At that point, interest in koi exploded throughout Japan. The hobby of keeping koi eventually spread worldwide. They are now commonly sold in most pet stores, with higher-quality fish available from specialist dealers