New World Encyclopedia - Koi
Sometimes nothing replaces the encyclopedia for facts and new knowledge. For instance; I did know that it was not until 1914, that the interest in koi really took off in Japan. Did you?
"Koi is any of the ornamental, domesticated varieties of the common carp, Cyprinus carpio, of the Cyprinidae family, a freshwater fish characterized by a forked caudal (tail) fin, barbels, and a wide variation in color and patterns, from solid to multicolored, and from dull gray, black, and white, to red, yellow, orange, blue, and metallic (gold and silver) colors. Koi (鯉) is known as nishikigoi (錦鯉) in Japanese, meaning "brocaded carp" or "colored Koi.
...The outside world did not become aware of the degree of development until 1914, when the Niigata koi were exhibited in the annual exposition in Tokyo. At that point, interest in koi exploded throughout Japan."
https://www.newworldencyclopedia.org/entry/Koi