It has been popular with Japanese people for a long time as an ornamental fish, and medaka with improved varieties such as medaka are widely distributed, and more than 500 varieties have been confirmed as of now.
It is also used in scientific research for various purposes.
It was first reported to the Western world in 1823 by Siebold, who came to Japan during the Edo period.
Philipp Franz Balthasar von Siebold
Image from Wikipedia
In recent years, medaka has been improved in variety, and there are hundreds of varieties.
The selective medaka is mainly called "Kai Ryo Medaka" in Japan.
(kai ryo means selective, improved, etc)
Medaka is Oryziinae （Subfamily:） Oryzias（Genus） Japanese rice fish (O. latipes)
Oryzias is a genus of ricefishes native to fresh and brackish water in east and south Asia.[4]
From : WIKIPEDIA (https://en.wikipedia.org/wiki/Oryzias）
English : Rice fish , Killifish