Japanese rice fish

The Japanese rice fish or medaka (Oryzias latipes) is a small, adaptable adrianichthyid native to East Asia, including Japan, Korea, eastern China, Taiwan, and parts of Southeast Asia. It inhabits a wide variety of shallow, vegetated waters including rice paddies, ponds, oxbows, agricultural canals, and tidal mangrove swamps, where it tolerates both freshwater and brackish conditions. Males reach a maximum standard length of approximately 3.6 cm and are distinguished from females by their elongated, filamentous dorsal and anal fin rays. The medaka has been kept in captivity for centuries, first in Japan and later worldwide, and has also been an important model organism in genetic research. This is a temperate to subtropical species that does best at cooler temperatures between 16 and 22 °C and should not be maintained permanently in heated tropical aquaria, as prolonged exposure to warm conditions shortens its lifespan. It is a micropredator that feeds on small insects, worms, and crustaceans in nature and accepts quality dried foods supplemented with live and frozen fare in captivity. Peaceful and schooling by nature, it should be kept in groups of at least 8 to 10 specimens in a planted aquarium with base dimensions of at least 45 × 30 cm.