What Size and Type of Aquarium is Best for Medaka? How Many Liters Per Fish?

This article explains which size and type of aquarium is recommended for medaka.

Medaka are robust and tolerate poor water quality well, but keeping them in too small an aquarium can lead to disease. Therefore, it is crucial to keep them in a generously sized aquarium.

Especially when you have just purchased medaka and introduced them to an aquarium, they are prone to stress and death, so it is better to keep them at about one fish per two liters rather than one liter per fish.

Use as Large an Aquarium as Possible for Medaka

Aquarium Size (Capacity) For breeding For keeping
Less than 30cm (5-10 liters) 2-4 fish 5-10 fish
30cm (10-12 liters) 4-6 fish 10-12 fish
40cm tank/30cm cube (20-24 liters) 10-12 fish About 20 fish
60cm (56 liters) 20-30 fish About 50 fish

The above are common commercially available aquarium sizes and the appropriate number of medaka for each.

It is generally recommended to use as large an aquarium as possible. Although it is often said that medaka require one liter per fish, in reality, having two to three liters per fish reduces issues.

While medaka are considered easy fish, that is mostly true when kept outdoors; indoor keeping can be quite challenging. Particularly just after setting up an aquarium, water quality can deteriorate quickly, so it’s advisable to start with a slightly larger aquarium.

Gradually Increase the Number of Medaka

Medaka are sensitive to sudden environmental changes, so introducing many fish to the aquarium at once can lead to high mortality.

Therefore, even in a large aquarium, start with only a few medaka and wait for the beneficial bacteria to increase before adding more.

For about two weeks after setting up the aquarium, keep only a few medaka and gradually increase their number to avoid issues.

Recommended Medaka Aquariums by Size

Under 30 Centimeters

If you have only a few medaka, a tank size of less than 30 centimeters is sufficient. The aquarium sets pictured above have a capacity of about 5-6 liters but come equipped with filters, food, dechlorinator, and other necessities for keeping medaka.

If the aquarium is under 30 centimeters, it can house approximately 2-3 medaka. Naturally, if they are fry or juveniles, more than ten can be kept.

Medaka Genki Easy Aquarium Set


There are also small aquarium sets with integrated lights and filters, which are convenient for beginners because there’s no need to buy equipment separately.



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