Japanese Rice Fish

The Japanese Medaka has been cultivated in Japan for centuries, appearing in artwork and literature as a symbol of summer ponds and rice paddies. It is one of the first vertebrates to have been sent into space and has been used extensively in developmental biology research.

In the aquarium medaka are undemanding, peaceful, and active near the surface. Their near-transparent bodies allow internal organs and sometimes developing eggs to be seen in females. They tolerate a remarkably wide temperature range from 10°C to 28°C.

Medaka breed very readily — females carry strings of fertilised eggs attached to their vents for several hours before depositing them on fine plants. In warm conditions a new generation hatches every few weeks.

Water: 10–28°C, pH 6.5–8.5, GH 4–20; extremely adaptable; no heater needed in most homes. Tank: minimum 20 L nano tank, surface plants such as frogbit, floating plants for egg attachment. Feeding: omnivore — micro-pellets, flake, frozen baby brine shrimp, cyclops, daphnia. Breeding: females carry egg strings then attach them to plants; eggs hatch in 10–14 days at 20°C. Compatibility: peaceful; ideal with other temperate nano species, small shrimp, and snails.