Winter Care Guide for Medaka | Outdoor Cultivation Tips

Winter Care Guide for Medaka

Medaka are hardy fish well-adapted to Japan's four seasons. They can survive summer heat and winter cold—this image itself is true, but many people make the mistake of assuming they can "survive winter without doing anything." It's not uncommon to find the entire population gone when spring arrives.

For medaka to successfully survive the winter, it's important to prepare their environment before water temperatures drop. This guide breaks down overwintering preparation into easy-to-follow steps that even first-time medaka keepers can implement.

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Understanding How Medaka Overwinter

Medaka are cold-blooded animals, so as water temperature drops, their body temperature falls and their activity level decreases dramatically. When water temperature falls below 10°C, their movements slow noticeably, and below 5°C they enter a "dormant state," remaining motionless at the bottom of the container.

This state is not "death-like" in the true sense, but rather an energy-saving mode that minimizes energy consumption. With their metabolism slowed, they no longer need to eat, and digestive activity nearly stops.

Even if water surface freezes thinly, the bottom water is unlikely to fall below 0°C, allowing medaka to survive. However, they cannot survive if the entire container freezes solid. The key to overwintering care boils down to two points: "prevent the bottom from freezing" and "avoid sudden temperature changes."

There are slight differences in cold tolerance between medaka varieties, but the basic concepts of overwintering care apply to all types. Our medaka selection features many individuals from domestic breeders with proven overwintering track records, so check it out when choosing your variety.

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Timing and Method for Stopping Feeding

The first step in overwintering preparation is managing food.

When water temperature drops below 15°C, reduce the number of daily feedings and feed smaller amounts. When water temperature falls to 10°C or below, stop feeding completely.