Javanese ricefish

The Javanese ricefish is a small, hardy surface-dwelling species widely distributed throughout Southeast Asia, from Peninsular Thailand and Malaysia through Singapore and Indonesia, including Sumatra, Java, Borneo, Bali, Lombok, and Sulawesi. Its common name derives from its tendency to inhabit rice paddies and shallow coastal waters, and like other members of the family Adrianichthyidae, it is noted for its unusual reproductive strategy — females carry a cluster of eggs externally near the vent for several days until the embryos hatch. Reaching only about 3.5 cm, these are subtle fish with a semi-translucent body that blends into their natural environment, making them ideal nano-aquarium residents.

Javanese ricefish are particularly interesting for their tolerance of a wide salinity range. In nature they are typically found in coastal brackish streams, mangrove swamps, and pools, though they also occur in freshwater habitats. This adaptability makes them suitable for a variety of aquarium setups, from pure freshwater to low-end brackish. The minimum tank size for a group of six or more is about 40 litres, with a footprint of at least 45 × 30 cm. They thrive in densely planted aquaria with gentle filtration, and a tight-fitting lid is essential as they are known jumpers. Water temperature should be maintained at 24–29°C, with a pH of 7.0–9.0 reflecting their coastal, slightly alkaline natural habitat.

A peaceful shoaling species, the Javanese ricefish does best in groups of six or more where the subtle hierarchy of males displaying to females becomes apparent. They are omnivorous and accept finely crushed flake, micro-pellets, and small live or frozen foods such as brine shrimp nauplii and daphnia. Their small size and peaceful demeanour make them excellent companions for other nano fish like dwarf rasboras, small shrimp, and similarly-sized livebearers. They are one of the easier ricefish to breed in captivity, with the egg cluster on the female clearly visible — eggs can be gently removed to a separate container for rearing. With good care, they typically live two to three years.