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How To Care For Your Marimo Moss Ball

How To Care For Your Marimo Moss Ball

Marimo moss balls are one of the most interesting plants on the planet. They are rare growths where algae from the species Aegagropila linnaei grow into large velvety green balls. They can be found in Japan and Northern Europe, primarily in lakes and rivers. The movement of the water causes them to gradually become spheres, and can stay like this for quite some time.

Marimo moss balls are simple to care for, so they are a good option when you want to start your indoor plant garden. It is common in Japan for young children to have these as “pets” since they have minimal requirements to survive. There is even a festival in Japan every year to celebrate these rare growths. If you are looking for a unique plant that will 100% be a talking point for all who come across it, the Marimo moss ball is the plant for you.

How Do I Care For A Marimo Moss Ball?

marimo moss balls in a close up image of an aquarium. there is a blue and yellow fish swimming around the moss balls.

Marimo moss balls provide a great visual and functional aspect to any aquarium tank.


You should start with the light for a Marimo moss ball. Medium indirect light is most important when finding a home for your plant. Be sure to avoid direct sunlight as that will cause your marimo moss ball to burn, have brown patches and pieces of dead tissue. If you are unable to find a good spot for your moss ball by a window, check out grow lights like these from Soltech Solutions.


To keep your Marimo moss ball’s water fresh and healthy, change it once every two weeks. This allows the tank to remain free from other algae or organisms that can possibly steal sunlight and nutrients from the moss ball. If your water level is noticeably lower in seasons such as summer where water evaporates more in the higher temperatures, change it once you notice a significant drop in water level. You can use normal tap water that has sat in open air for about 24 hours, when switching the water in your tank.


If you need to transport your Marimo moss ball to a new enclosure, or to a new home all together, it is possible to have it live outside of the water. By placing your moss ball in a plastic bag, a glass or plastic jar, you can keep your moss ball moist and protected from drying out.


You may wonder whether fish in your tank may find this velvety, green ball too good to resist, but most of the time fish and moss balls live in harmony. If you do happen to notice your fish pecking at the moss ball, you can separate them. However, for the most part, moss balls are able to absorb nitrates in the water as well as filtering the water. This will be beneficial for your tank, so if you see that your Marimo moss balls and fish can live in harmony, you can leave it in there permanently.

Where Can I Find A Marimo Moss Ball?

a glass jar terrarium with a cork lid sitting on a rocky beach in front of a sunset. The terrarium features a marimo moss ball and a sea shell.

The Terrariums that provide are a great way to begin your parenthood of these interesting pieces of nature.

This website offers Marimo moss balls in terrariums. This is a great place to start your journeys with Marimo moss balls as these little jars are smaller than large fish tanks. They will be easier to maintain and keep clean.

Make sure that you can get a healthy moss ball, otherwise you’ll be doomed before you even start. A healthy marimo moss ball is vibrant and green. If you see brown or black spots, it isn’t as healthy as it can be and will most likely give you trouble.

Moss balls can also be found at different pet stores, especially ones that specialize in marine species.

What Problems Can I Have With A Marimo Moss Ball?


a brown marimo moss ball

Moss balls that are brown are likely unhealthy.

When you search for Marimo moss balls online, you’ll likely come across pictures where they look luscious, green, velvety and soft. Almost like a little ball of summer grass or a nice soft rug. It will be easy to notice browning on your Marimo moss ball, since its appearance will vary from this typical luscious green look.

This likely means that you have it in direct sunlight, so move it to an indirect source of light and if it doesn’t heal itself, add some ocean salt to speed up the healing process. If none of these seem to be the cause, learn more about why plants brown or yellow.


a marimo moss ball floating above a group of moss balls in a tall square glass.

These moss balls are floating in their tank, it is important to pop the bubble within to allow them to sink again.

You may notice your moss ball to float, but have no fear, this is entirely normal. Air bubbles have most likely accumulated inside the ball. If you pull it out of its tank and gently squeeze it, you will pop the air bubble. It will usually sink after a day or two after the bubble has popped.


a mishapened marimo moss ball. the moss appears as a flat piece of moss rather than a ball.

Misshapen Marimo moss balls defeat the purpose of you purchasing them. Make sure to agitate the water to keep them round.

More likely than not, you have purchased a Marimo moss ball due to their shape. They are unique and fascinating, so you would hope that your moss ball stays exactly that: a ball. In nature, Marimo moss balls become and stay spherical due to the constant movement of water in the rivers and lakes.

If you keep Marimo moss balls in an aquarium with no movement of water, they can become misshapen, and lose their round, spherical shape. Try to agitate the water in your tank to simulate waves in a natural habitat.

Invasive Species

a hand holding a marimo moss ball with a zebra mussel inside

A zebra mussel found in a Marimo moss ball.

Zebra Mussels are an invasive species, originally from the Caspian Sea in Europe, that are capable of wiping out endangered species in freshwater environments.

As can be the case with any habitat for plant or animal species, invasive species can spoil your fun with Marimo moss balls. Last year the Department of Wildlife Resources in Virginia released a statement saying that Zebra mussels had been found in a wide range of stores that sell the algae.

This is a big problem for your local environment as Zebra mussels are an invasive species. They are capable of filtering a quart of water a day, and with their quick rate of reproduction, they can strip a waterway of nutrients in no time. Local governments and businesses have invested billions of dollars over the past 40 years trying to limit their spread and destruction of local wildlife and ecosystems.

If you suspect your Marimo moss ball has been infected by an invasive species, it is recommended that you remove your moss ball immediately. You have 3 options to dispose of them:

  • Put your moss ball in a plastic bag and freeze it overnight.
  • Boil your moss ball.
  • Put your moss ball in a bleach solution overnight.

After doing one of these treatments, bag your moss ball and throw it in the garbage. Thoroughly clean your tank to ensure that no microscopic eggs have been left behind, which would result in another infestation.

What Is The Marimo Festival?

Created in 1950, the Marimo Festival takes place in Lake Akan, Japan. The main purpose of this festival was to help save the endangered marimo algae that reside in Lake Akan. It is a great cultural experience, as those who attend it are able to witness the customs of the indigenous Ainu people. Learn more about the Marimo Festival here.