Medaka, Japanese killifish

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It is distributed in Asian regions such as Korea, Japan, China, and Vietnam, and lives in groups in freshwater areas such as ponds, agricultural waterways, and reservoirs with shallow and calm waters. In particular, it is highly resistant to changes in temperature, water quality, and salinity of the surrounding environment, and killifish swarms that have been swept away to brackish areas adjacent to the sea due to floods or typhoons survive.

It is a very small fish with a body length of about 5cm, and its body is translucent so that the internal tissues are slightly visible. Unlike females, males have a split edge on their dorsal fins, so you can distinguish between sexes.

Breeding occurs from May to July, but if you keep the fish as an ornamental fish, you can breed it all year round if you set the water temperature to around 20 degrees. The female attaches the eggs to the waterweed. The lifespan is usually 1 to 2 years, but it is known that they can live up to 3 to 5 years in captivity.
It feeds on zooplankton, organic matter, and small insects. In particular, they are often released for ecological mosquito control because they eat worms well and are somewhat resistant to contamination, so they can live in grades 2 and 3 waters. Loach also eats caterpillars well, but killifish is far superior in the amount of predation compared to body weight. Other fish species prey on 30-40 fish per day, but killifish can eat up to 150 per day.

Source : namu.wiki