Marimo Moss Ball – Care, Growth, Propagation, Light

The marimo moss ball (Aegagropila linnaei) plant is a species of green algae that grows into a spherical ball. Marimo balls are fascinating and beautiful, and they have become quite popular in aquariums and display tanks.

You can even keep them in bowls or vases if you are an enthusiast of indoor gardening. The plant is also popular because it sucks up impurities in the aquarium and it offers a surface area for the colonization of beneficial bacteria. Small creatures like shrimps eat the particles of food on the balls while bettas play around with them.

Marimo Moss Ball Origin

The plant was given the name “marimo” by the Japanese scientist Tatsuhiko Kawakami. The Japanese term marimo loosely translates to ‘seaweed ball.’ The plant was identified in Lake Akan in Japan but other populations inhabit freshwater lakes in Estonia, Iceland, and Scotland.

The plant was recognized as a Japanese national treasure in 1921, which sparked its harvesting as it became more and more coveted. It is recognized as a good-luck charm in the country, and it is often passed down generations as a heirloom. The plant can live for 200 years, and they grow bigger with time.

By the 1940s, the plant was critically endangered in Japan due to overharvesting and the construction of a hydroelectric power plant on the Akan River. It thrives in shallow waters, and it is, therefore, impacted by reducing water levels.

The Marimo festival was subsequently established in 1950 and the local government created the Marimo Exhibition and Observation Center.

Marimo Moss Ball Appearance

The balls consist of strings of algae that form spheres as they roll around in lakes. There is no central kernel in the ball as it is all solid algae growing from the center. In the wild, the plant grows slowly, typically at a rate of 5mm a year. They will grow faster if given fertilizer in an aquarium and they can reach 8-12 inches in diameter.

The sphere is entirely green to encourage photosynthesis as they roll around. It moves to the water’s surface when there is low oxygen and sinks when the water is saturated.

There are dormant chloroplasts in the ball that will become active when the ball is broken apart. The balls divide on their own to form new colonies. You can cut a marimo moss ball into two and roll them with your hands to build new plants.

Marimo Moss Ball Water & Light Requirements

In the wild, marimo moss balls thrive in cold lakes, but they are adaptable to the standard ranges in aquariums. The ideal temperature would be between 72-78 °F. The plant can quickly melt and begin to rot if the temperatures exceed 80 °F.

If you live in a hot locality, you may have to get an aquarium chiller or relocate the tank to a cooler area. Some aquarists place the bowl in the refrigerator when it’s hot or add ice cubes to the tank.

Keep the plant in areas with indirect sunlight and medium light. The balls can quickly turn a brown color if they are exposed to direct sunlight. Intense light will also heat the water and create an inhospitable environment for the plant.

Normal household lighting will be adequate for the plants. You can install standard aquarium lamps and lights but do not use high-intensity LED fixtures.

Marimo balls can grow in saltwater tanks with a salinity of up to around 1.015. You can use a salinity meter to ensure that the salinity levels do not become too high. Some aquarists also add little doses of salt to the aquarium when the balls start turning brown

Marimo Moss Ball Maintenance

Water changes will discourage dirt and impurities from accumulating on the plant. If you are keeping the marimo balls alone in a container, you can perform 50% water renewals every two weeks. Frequent changes are necessary if the marimo is kept with other plants and fish.

You should condition the renewal water with a de-chlorinator to remove the chlorine present in tap water. The plant will be fine with conditioned water, but you may have to treat it if there are fish in the tank.

Marimo balls should be cleaned often as they attract impurities and debris as they float around. It will be time for a wash if you notice the balls turning grey and brown. Washing the plant is as easy as squishing the balls in clean water or swishing it back and forth. A firm grip on the plant will prevent it from disintegrating.

Marimo balls are prone to getting sick even if the water conditions are ideal. When this happens, leave it in the refrigerator overnight, and move it to an area with direct sunlight in the morning. You should observe a significant improvement in two to three days.

You should keep rolling the balls every other week to ensure that it is receiving light evenly. Any side of the ball that is not receiving enough light will soon start turning brown. If you have multiple balls in the same container, ensure that no ball is blocking the other’s access to light.

When keeping your marimo moss balls in a community tank, you should get fish and invertebrates that will not kill them. Goldfish are aquarium favorites, but their grazing habits are not ideal for the moss balls. Pleco fish are also notorious grazers.

Bettas have been kept successfully with marimo balls, as have snails and small shrimp.

Marimo Moss Ball Propagation

The plant propagates by division, and you can easily create a colony in your aquarium. To start, remove the ball from the container and squeeze out excess water.

Cut the sphere in half as they do not have a central structure. Tie thread on the ball as you would wrap a ribbon and knot it neatly.

Put the cuttings back into the container and ensure that the water parameters are ideal. Turn the balls once a week or more to ensure that they are receiving light in an even fashion.

You should also roll them around so that they can attain the spherical shape.


Marimo moss balls are lush spheres of green algae that bring life to any freshwater set up. They are quite easy to maintain, as long as you do not expose them to direct sunlight and maintain the temperature below 80 °F.

Aquarium Plants   Updated: June 17, 2020
avatar Hello, my name is Fabian, and I am the Chief Editor at Aquarium Nexus. I have over 20 years of experience in keeping and breeding fish. The aquarium hobby brings me immense joy, and I take great pleasure in sharing my experiences with others.

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