Javanese Medaka

Oryzias javanicus is a euryhaline ricefish native to coastal areas of Java, Sumatra, and the Malay Peninsula, where it inhabits estuaries, mangrove-adjacent waters, and freshwater streams near the coast. Its golden-tan colouration is modest but appealing, and it shares the upturned mouth and flat dorsal profile characteristic of all medaka.

The euryhaline nature of this species sets it apart — it can be acclimatised from fresh water to brackish water up to 10 ppt salinity, making it a versatile candidate for lightly brackish Southeast Asian biotope aquariums. However, it is equally content in standard fresh water with neutral to slightly alkaline pH.

Breeding is straightforward. The species is prolific and eggs are deposited on fine vegetation or spawning mops. Fry are robust and accept micro nauplii from hatching. This is an underused species well suited to brackish nano aquariums or coastal biotope setups.

Water: 22-28°C, pH 6.5-8.0, soft to hard — tolerates fresh to light brackish (up to 10 ppt). Tank: 30 L, floating plants, can include a small amount of marine salt for coastal biotope. Feeding: surface micro pellets, frozen baby brine shrimp, and daphnia. Breeding: prolific egg scatterer; easy in any correct water parameters. Compatibility: peaceful; good with brackish-tolerant gobies, small livebearers, or fresh companions.