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Caring for Marimo Moss Balls: the Perfect Gift for Plant and Aquarium Enthusiasts

Caring for Marimo Moss Balls: the Perfect Gift for Plant and Aquarium Enthusiasts

Marimo moss balls are one of the most interesting plants on the planet. Not actually moss, they are rare growths where strings of 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?

<img src="images/image1.jpg" alt="marimo moss balls in a close up image of an aquarium. there is a blue and yellow fish swimming around the moss balls." style="float: none;">

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


It is important to first consider the lighting conditions your Marimo moss ball will be exposed to. Medium indirect light is optimal 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. Soltech offers a variety of options, like the Grove™ Grow Bar Light, to display your aquatic setup like an art exhibit.

The Grove is also a great selection as it can be easily adjusted without renovating your setup. Too much direct light is also detrimental to the growth of these plants. If your moss ball is beginning to become discolored, consider whether you should look into dining your light, or adjusting it to be less direct.


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. Of course, if you keep other organisms in with your moss balls, you will defer the water change to best suit their needs.

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, but moss balls do thrive in brackish water. Add some aquarium salt to mimic the natural conditions of the slightly-salinated bodies of water Marimo thrive in. When switching the water in your tank, be sure not to avoid any chlorinated water samples.


Cleaning your Marimo moss balls themselves is actually a fairly simple process, but should not be neglected. You may keep shrimp or a breed of small fish species to clear your Marimo of different algae species which develop on its surface. However, if your Marimo moss balls are being kept alone, or you do not keep a species of creature which will symbiotically clean its surface, you can complete the cleaning process yourself by squeezing out the moss ball with your hands. Repeat this process several times.

It is important to note that this may slightly alter the shape of your moss ball. Not to worry! Simply roll the ball in your hands several times to help it retain its round shape. You will, of course, want to return it to its home in this state, as the main appeal of Marimo is its unique shape.


It is very important to note that Marimo moss balls actually prefer cooler temperatures. Therefore, it is important to ensure the water does not rise above 76º Fahrenheit. If you find that your moss ball is developing brown spots, this may be a result of overheating. If this is the case, place your moss ball in the refrigerator for up to 24 hours. If you can not ensure cooler conditions for any reason, repeat this process every time you feel your moss ball is becoming susceptible to the temperature.


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. People often pair betta fish, or “fighting fish,” with Marimo moss balls. These fish will often use the moss balls as a “couch” of sorts, or will even play with them.

If you do happen to notice your fish pecking at the moss ball, you can separate them. However, This behavior usually just results in the Marimo keeping its shape. As well, moss balls are able to absorb nitrates in the water and even filter 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 set back before you even start your own journey. 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. However, you must be careful, as these moss balls can be diseased, infested, or even dead upon purchase.

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. You will have more control over the lighting conditions if you use a grow light, like the Aspect™ from Soltech. If changing the light does not allow the moss ball to 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 are brown or yellow.

Nitrogen deficiency can present issues in these plants. They become brown and yellow, and can become susceptible to illness. They will begin to smell, and perhaps shed. You should also be mindful of these plants developing a slimy texture, especially as you continue to clean it.


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

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. As with the cleaning process, make sure to “reshape” your moss ball before returning it to its original bowl/tank.


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

If you want to further prevent your Marimo moss balls from becoming misshapen, make sure to agitate the water they are kept in frequently, in order to keep them round. In nature, Marimo moss balls become and stay spherical due to the constant movement of water in the rivers and lakes. You must mimic these conditions if you would like them to remain spherical. Try to recreate waves as best you can, when stirring the water.

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.


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

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 with bleach, 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 three day festival is to help save the endangered Marimo algae that reside in Lake Akan. It is a great cultural and educational experience, as those who attend it are able to witness the customs of the indigenous Ainu people, as well as appreciate the beauty of nature and man's role in preserving it.

At this celebration, you will participate in dances and parades led by Ainu priests, following a more traditional and reserved blessing by a priest. You will be met with a multitude of options for pastimes, such as hot springs and cruises to see the moss balls themselves.

Why choose Marimo Moss Balls?

Marimo Moss balls are the perfect gift for those looking to dabble in hydroponics! Maybe you know an aquarium enthusiast, who wants to introduce some greenery to his fish’s home. Or, maybe the child in your life has been begging for a trip to the pet store for a goldfish, but you’d like to start off with something a little lower responsibility for them first.

Moss balls can live for up to 200 years. They are traditionally passed down between generations in Japanese families. This is a wonderful tradition to share with your loved ones, as well. Watch as each person adapts their specimen to their lives in their own unique ways, from the vessel they store it in, to the company they keep it with. Allow them to tell their own unique story with this species, as you yourself care for and maintain your own aquatic ecosystem!