The Japanese rice fish (Oryzias Latipes) are one of the most popular pet fish that people have raised in aquariums for a long time. They are also known as the Medaka or the Japanese killifish. They come from They are very small in size and are famous for their beautiful colors.
They are characterized by their semi-transparent orange or gold color and some of them have blue eyes. The Japanese citizens have been raising them in aquariums since the seventeenth century.
After that, they have spread to Korea, Vietnam, India and Pakistan. The Japanese rice fish have an elongated body, and the back has a slight resemblance of an arch.
One of the characteristics that make them very beautiful is that their bodies glow in the dark. The most famous kinds of the Japanese rice fish are the gold and moonlight medaka. The gold medaka existed since ancient times, whereas the moonlight medaka are a new bred color morph.
Naturally, the Japanese rice fish live in the rice paddies of Japan. This is the ideal place for fish under the “Oryzias” genus. The main reason is the inexistence of predators. Another reason is that the water temperature is suitable for them.
Recently, scientists used these fish in experiments for biological development. A group of medaka was sent to outer space, as some scientists believe that they can breed faster and easier there.
 
The Japanese rice fish live in groups. These groups are referred to as schools. Despite this fact, sometimes they tend to move on their own or in pairs. The Japanese rice paddies are the natural habitat for these fish.
So, basically you need to create a replica of this environment. Due to their small size, they don’t really need a large aquarium to live in. The tank size has to be at least ten gallons. In some cases, a larger tank would be a better option. This shall provide a good amount of space for them to move freely.
You will need a good filtration unit. The Japanese rice fish can’t survive in dirty or polluted water. Therefore, you should change the water in the aquarium regularly, as it is much healthier for them.
The aquarium needs a firm lid, because these fish have great mobility and can easily jump out of the aquarium. Surely, you wouldn’t want to have fish jumping out of the tank and roaming on the floor.
It would be recommended to have a spongy lid on top of the aquarium to enrich the water with air. Drilling a ¼” tubing or air inlet is a good option if the lid doesn’t provide the needed air support.
 
In addition, a well-lit environment is optimal for them. Since the Japanese rice fish naturally live in rice paddies, where there is shallow water, they receive a considerable amount of sunlight. 
The substrate of the aquarium can be covered with gravel or sand. Some plants and small driftwood would be nice for them to hide. These accessories would make them feel like they’re living in their natural home.
Due to the vast difference between all fish, each group settles in a certain place under the water surface. The durability and homeostasis of the fish are two major key factors to determine the needed water specifications.
Some fish live in shallow water only. And other types find pleasure and comfort in living way deep beneath the sea, where the pressure is too high.
Brackish water is the optimum type of water for the Japanese rice fish. In nature, these fish tend to escape from the rice paddies and into the ocean for a little bit. However, they can live perfectly in freshwater, since they can be found in rivers.
They prefer to live in cold environment. The suitable water temperature for the Japanese rice fish ranges from 64 to 75 Fahrenheit. The pH of the water should be 7.0 to 8.0.
Make sure that the water is almost steady inside the aquarium, as they prefer to live-in slow-moving water.