What Should You Put in a Medaka Tank? [Soil, Aquatic Plants, Shrimp, Snails, etc.

There are many things that are good to put in a medaka tank. Of course, medaka are hardy fish and can be kept without adding anything.

However, there are some things that, when added to a medaka tank, can reduce the risk of disease or increase the number of eggs laid.
I also use various items in my medaka tanks. Based on what I have actually tried, I will introduce items that are good to put in a medaka tank. If you are looking for things to add to your medaka tank, please refer to this!

7 Recommended Items to Put in a Medaka Tank

Here are 7 recommended items to put in a medaka tank.

Soil (Akadama Soil, Kurodama Soil)

One of the most versatile items to put in a medaka tank is soil.
Soil has various effects beneficial to medaka, such as absorbing impurities from the water and increasing water-purifying bacteria.
Additionally, soil contains nutrients like minerals that promote the healthy growth of medaka.
However, if you layer the soil too thickly, anaerobic bacteria can develop, leading to disease, so it is better to lay it thinly or place it in a net. I use soil primarily for nutritional purposes, so I sprinkle a pinch of soil into the tank once a week. I believe this alone has a positive effect.

Adding soil to a medaka tank also makes the water clearer, enhancing its aesthetic value.


Oyster Shells and Coral Sand

Many people also add oyster shells or coral sand to their medaka tanks. Oyster shells and coral sand help make the water more alkaline. Medaka are believed to prefer alkaline water and are less likely to get sick in such conditions. Many people add coral sand or oyster shells to their medaka containers.

Sponge Filter

Among the items good to put in a medaka tank, the sponge filter is particularly recommended.
Sponge filters are high-performance filtration devices that do not create water currents, making them ideal for medaka, which are not strong swimmers.
Additionally, sponge filters do not absorb water, so they do not suck in fry or eggs. For this reason, top medaka breeders often have sponge filters in their tanks.


Aquatic Plants

It is also good to add aquatic plants to a medaka tank. However, aquatic plants can be surprisingly difficult to grow, so it is better to choose hardy species like anacharis or hornwort.
In breeding tanks for broodstock, adding aquatic plants may complicate egg collection as the eggs are often laid on the plants.
Therefore, it is better not to add aquatic plants to breeding tanks intended for egg-laying.
In fry and juvenile tanks, it is recommended to add plenty of aquatic plants as they provide hiding places and serve as habitats for bacteria that can be food.



Snails are a must-have in medaka tanks. Snails help clean up uneaten food, reducing the frequency of water changes.
This is especially important in breeding tanks or fry tanks where a lot of food is needed, leading to uneaten food.
By adding snails, the uneaten food is cleaned up, preventing water pollution.
In my tanks, I have both ramshorn snails and pond snails. Thanks to them, there is no uneaten food even if I overfeed a bit, making them very convenient.



Shrimp are also good to add to a medaka tank. While you can manage without shrimp if you have snails, shrimp have unique roles.
They eat filamentous algae that may grow in the tank.
Ramshorn snails and pond snails do not eat filamentous algae, so adding shrimp can help keep the tank clean.
Amano shrimp are the best at algae removal, but they may eat fry or eggs and grow quite large, making them unsuitable for small tanks. Therefore, I use Neocaridina shrimp in my medaka tanks.


PSB (Photosynthetic Bacteria)

PSB, also known as photosynthetic bacteria, are said to have a water-purifying effect. Additionally, they contain various nutrients and are used as food for fry and adult fish.
Adding PSB to the tank daily not only stabilizes the water quality but also helps prevent fry from starving.
Many famous medaka specialty shops like Seirakuan use PSB. I also add PSB daily to my fry tanks.



Lastly, X-babel is a good addition to a medaka tank. X-babel contains vitamins and minerals, and adding one drop per 10 liters is said to help prevent diseases in medaka.
However, adding this to all tanks every day can be expensive, so I only add it to breeding tanks.
While it does not guarantee curing diseases or significantly increasing the number of eggs, I have had instances where adding it to a reluctant female’s tank triggered egg laying, so it may act as an egg-laying switch.
Of course, its priority is lower compared to the other six items, but if you have problems with medaka not laying eggs, it might be worth trying.


Things that are good to add to a medaka tank include soil, sponge filters, aquatic plants, snails, shrimp, and PSB.
However, as explained at the beginning, medaka are hardy fish and can be kept without any of these items.
Especially when kept outdoors, they can be raised without an air pump or other equipment.
Nevertheless, adding these items to the tank can significantly lower the difficulty of keeping medaka, so give it a try!


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