seatrench:

The Japanese Rice Fish (Medaka) is a popular aquarium pet in Japan due to its hardiness and bright colouration.  They are also notably used in science,  being the first vertebrate to breed in orbit,  producing a batch of healthy fry aboard the Space Shuttle Columbia in 1994.  They are also used as a popular model fish in transgenics,  and have been bred to glow in a variety of fluorescent colours,  as well as the ability to secrete human hormones for medical use.

(source)