What is a Medaka?

A medaka is a fish of the Adrianichthyidae family and Oryzias genus that is usually referred to as ricefish. It is sometimes called the Japanese killifish. In addition to Japan, it is found in most of Asia, including Korea, China, and Vietnam, usually in ponds, marshes, and rice paddies.

The medaka is a very small fish, usually reaching about 1.6 inches (4 cm) in length. Its body is very slender and elongated, with an arched back. Its very small size does not make the medaka a popular fish for fishermen, but its bright coloration and appearance has long made it a favorite of aquarium enthusiasts. In nature, the fish is usually brown or yellowish gold. Captive breeding has increased their color range, with white, yellow, or pure orange variations not uncommon.

As aquarium fish go, the medaka is a fairly hardy fish that can survive in a wide range of water conditions. Water temperatures can vary from 65 to 75 degrees Fahrenheit (18 to 24 Celsius), and pH levels can range from 7 to 8. As long as it is mixed with non-aggressive fish of a similar size, it makes a very good fish for community tanks.

Caring for the fish is also easy. The medaka will eat a variety of foods, from flake and freeze-dried foods to a wide range of frozen foods. Like many smaller fish, it prefers to have plenty of cover in the tank to hide when stressed. It also requires some degree of water movement, which can be provided by an air stone or filter.

The medaka is also a popular fish for researchers thanks to its hardiness and relatively quick breeding cycle. Medaka have been extensively used in environmental research. Tests involving carcinogenesis and related fields of study have been conducted on the fish in the past. Genetic manipulations on the fish have created captive-only variants of the fish, including a type that glows fluorescent green.

The use of the Japanese killifish as a research tool has even extended to outer space. In 1994, four medaka were taken aboard the USS Columbia space shuttle for a variety of tests, as they were the only fish species known to withstand micro-gravity. Not only did the fish thrive in the shuttle, but they bred, becoming the first vertebrates to produce offspring in space. The medaka kept aboard the Columbia laid 43 eggs, some of which hatched while still in space. All the fish that hatched both in space and back on Earth exhibited no noticeable side effects from their travels.

A Medaka, also known as the Japanese rice fish (Oryzias latipes), is a small, freshwater fish native to East Asia. It's popular in aquariums due to its hardiness and ease of care. Medakas have a rich history in scientific research, being one of the first vertebrates to breed in space aboard the Space Shuttle Columbia in 1994.

Medaka fish thrive in a variety of freshwater environments, from rice paddies to slow-moving streams and ponds. They are adaptable to different water conditions but prefer shallow, warm waters with plenty of vegetation. This vegetation provides them with food, shelter, and breeding grounds.

Caring for Medaka fish involves maintaining clean water with a pH between 7.0 and 8.0 and a temperature range of 64-75°F (18-24°C). They require a well-planted aquarium with space to swim and a gentle filtration system. A varied diet of small pellets, flakes, and live or frozen foods keeps them healthy.

Medaka fish are omnivorous and have a diverse diet. In the wild, they consume small invertebrates, zooplankton, algae, and plant matter. In captivity, they can be fed a mix of flake food, brine shrimp, daphnia, and bloodworms. Feeding them twice a day in small amounts is recommended to prevent overfeeding.

Yes, Medaka fish are an excellent choice for beginner aquarists. Their resilience to varying water conditions and simple dietary needs make them relatively easy to care for. Additionally, their peaceful nature and small size, typically reaching about 1.5 inches in length, make them suitable for community tanks with other non-aggressive fish.

Medaka fish are known for their ease of breeding in captivity. They are egg-layers, and with the right conditions, including a well-planted tank and stable water temperatures, they will spawn readily. The eggs attach to plants and hatch within a week. Raising the fry requires infusoria or specially formulated fry food until they can eat regular fish food.