Is Aeration Necessary for Medaka? Do You Need an Air Pump for Oxygen?

This article explains whether aeration is necessary for medaka. If you want to know whether it is essential to supply oxygen with an air pump when keeping medaka, please read on.

It is Better to Aerate Indoor Medaka Tanks

To start with the conclusion, it is better to aerate indoor medaka tanks. The reason is that using an air pump not only prevents oxygen depletion but also prevents water from becoming stagnant, improves water quality, and helps prevent diseases. Outdoors, the wind helps oxygenate the water, but indoors, where there is no wind, it is advisable to aerate when keeping medaka.

However, medaka consume less oxygen than goldfish and other fish, so it is possible to keep them without aeration. Therefore, if you are raising medaka as a hobby, an air pump is optional. However, if you want to keep medaka healthier, supplying fresh oxygen through aeration significantly increases the chances of success.

Outdoors, It Is Optional but Beneficial

When keeping medaka outdoors, an air pump is optional. Outside, the wind causes the water surface to move, allowing oxygen to enter the water. Therefore, unless you are keeping a large number of medaka, an air pump is unnecessary outdoors.

However, having an air pump does help stabilize water quality, and in the summer, there are instances where the container might suddenly become oxygen-deprived. In such cases, aeration can be beneficial if you have the equipment.

Benefits of Installing an Air Pump in Medaka Tanks

Here are the benefits of installing an air pump in medaka tanks. Firstly, aerating the tank to supply oxygen helps prevent oxygen depletion.

Unless you pack hundreds of creatures into the tank, medaka are unlikely to suffer from oxygen depletion. However, aeration in medaka tanks provides several benefits beyond preventing oxygen depletion.

Prevents Water from Becoming Stagnant

Aeration in medaka tanks helps prevent the water from becoming stagnant.

Without water movement, water deteriorates faster, and bacteria can easily proliferate. In contrast, aeration creates water flow, keeping the water fresh. Therefore, even for stored water, it is better to use an air pump to keep the water from deteriorating.

Activates Bacteria

By supplying oxygen through aeration in medaka tanks, you can activate bacteria and improve water quality. Bacteria that decompose ammonia are called aerobic bacteria and become active in oxygen-rich environments. In other words, aeration increases the population of beneficial bacteria in the medaka tank. In fact, tanks with air pumps tend to have cleaner water and fewer diseases compared to those without.

Products like Samurai EX, Bacteria Honpo, and Oshimada Water mention that aeration enhances bacterial activity.

Is a Filtration System Alone Not Enough?

Isn’t an external filter or other electric motor-powered filtration systems sufficient instead of an air pump? Note that internal filters (such as Suisaku Eight), sponge filters, and under-gravel filters are air pump-connected and thus provide aeration.

There are varying opinions on this, but my view is that it is better to have a separate air pump. Theoretically, shaking the water surface allows air to enter, so top filters or external filters should work like aeration. However, in my experience, even with a filter, aeration makes the medaka healthier, so I use an additional air pump.

Based on my experience, medaka tend to thrive better with additional aeration even if a filter is present. Therefore, I use only air lift-style filtration systems like sponge filters, which provide both filtration and aeration.


Aeration is optional for medaka tanks. Weak medaka might experience worsened health due to aeration because it activates not only beneficial bacteria but also pathogens like Columnaris bacteria.

However, Aeromonas bacteria are anaerobic and thrive in areas where aeration cannot reach, like the bottom substrate. Therefore, in the long run, aeration improves the tank environment. Moreover, Columnaris bacteria can be eradicated by treating medaka before introduction.

I always treat medaka before adding them to a tank with a sponge filter, and hardly any die. If you want to keep medaka healthy indoors, aeration is recommended.


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