The rice fish (Oryzias) have been in the focus of aquarists for several years. First the fantastically colored O. woworae were discovered on Sulawesi, then the Japanese Medakas (O. latipes) experienced a renaissance, because many interesting new breeding forms developed. Most species of the genus, which comprises more than 30 species, occur quite locally. Two species, however, have a wide distribution because they are so salt-tolerant that they can even tolerate pure seawater: Oryzias dancena and O. javanicus. They are therefore found in nature not only in fresh water, but also in brackish water and along the coasts of South and Southeast Asia.
We were able to import a nice number of wild Oryzias from Sumatra, which must have been one of the two species. Oryzias dancena and O. javanicus are very similar, females can hardly be distinguished. In O. dancena the males have silver-white fin seams, but lack the yellow stripes in the caudal fin that distinguish the males of O. javanicus. In both species the males develop long, free fin rays in the anal fin, the edge of which is smooth in the females. Our current imports could be identified as O. javanicus based on the above mentioned characteristics.
Basically it doesn’t matter which of the two species you care for, both are very pretty, peaceful, small (3-4 cm) and easy to care for. They are also easy to breed, the females carry the eggs in the form of grape-like bundles for a while before they shed them in plants etc., as is common with Oryzias. But as both species can crossbreed, the hybrids often have many deformations and are not breedable in the long run, it is better not to mix the two species in the aquarium.
For our customers: Oryzias javanicus has code 339703 on our stock list. Please note that we only supply wholesale.
Text & photos: Frank Schäfer