There has been a lot of linebreeding with these fish. They became very popular in Japana with the post trsunami power cut - they are hardy and very cheap to keep. They need a tank, a filter and a light, with no heater.
I'm unimpressed, but with linebred fish, that's no surprise. With their quick incubation, they are easy to manipulate and people who like selecting and linebreeding fish enjoy them. I've been expecting them to be marketed hard in places where energy costs are really high. They have a big place in the future of the commercial hobby
because they thrive unheated - tomorrow's guppies.
There are also 33 species in the Genus Oryzias. Some people still think there's the Japanese Medaka, and that's it. Some of the others are pretty, but you can'tgeneralize about their needs, as usual.
O. woworae is a cool species for its breeding. It is very odd, with its hanging egg clusters. Just as community fish, you see nothing but if you keep them alone they are something to think about. I kept and bred them for a bit, but they are a fish for people who like breeding and not just looking at tanks. Ricefish are perfect for communities.
I can see the usual name issue as all the species are called 'ricefish' in English, but as far as I know, "Medaka" is the name for the modified, increasingly sold community tank ones.