Marimo Moss Ball Care Tips

INSIDE : The best tips on how to care for Marimo Moss Balls! Including where to buy, their watering needs, light needs, the best containers and much more.

Marimo Moss Balls in jar

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Are plants your jam like like me?  You might be interested in a few of my Plant Care posts.

Oh friends, let me introduce you to the newest GREEN pet rock.  Every single time I share a glimpse of this new favorite plant, I get tons of questions about what these mystery things in a jar are… drum roll… Today I am sharing all I know about Marimo Moss Balls!

Let’s first start with a ittle bit of backstory on these awesome plants.


The Japanese word, Marimo, translates to “seaweed ball”.  Both Lake Akan, in Japan, and Lake Mývatn, in Iceland, have been declared as national parks and nature reserves to conserve marimo moss, which is a protected species in both countries.


Marimo Moss Balls are actually not a “moss” at all, they are actually a rare type of circular algae.  There’s no central pit or seed inside the moss ball – it is a solid algae, radiating from the center, growing outward very slowly at about 5mm per year.  However, in their natural habitats they’ve been known to grow to between 8 and 12 inches in diameter!  Can you imagine having a moss ball that big – how cool.

Marimo Moss Balls


In Japan, Moss balls are often passed down from generation to generation because they can live up to 100 years!  If you take care of yours and change out the water every one to two weeks… be ready for them to live a long time.

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I have had mine about a year now and have noticed one has slightly lost it’s super round shape. They live naturally in lakes and the gentle waves slowly rotate and roll them around into circles and they form into moss balls.

To make sure that the balls stay keep their round form and don’t flatten out, you’ll want to slightly swirl the water that you have your plant in.  When all the balls settle back to the bottom, they will rest on a different side than they had previously. This movement is similar to the gentle waves of a lake.  I try to do this once a day as I casually walk past the plant.

Need more creative plant related projects?  You might enjoy some of these.

Marimo Moss Balls in water

Okay, if you are completely intrigued like I was, then you’ll want to know

Where can I buy Marimo Moss Balls?

There used to be more places online that were selling Marimo Moss Balls. I’ve found they are still available at Etsy and it looks like Amazon is also selling them, as well.  

HOWEVER! I recently learned about the major issue with invasive Zebra Mussels on Marimo Moss Balls and the US Fish & Wildlife request that we dispose of ALL moss balls bought AFTER February 1, 2021. You can read more about the directive and steps they recommend for that, here.

Marimo Moss Balls

Can I have Marimo Moss Balls around fish?

Most fish can live in the same tank with Marimo moss balls.  However, a few types of fish and invertebrates may eat or damage the Marimo balls – Goldfish, some types of Plecostomus (Plecos), and large-sized crayfish.

How to Grow Marimo Moss Balls?

For marimo moss to thrive, the container should be kept in a cool place, out of the reach of direct sunlight.  To best mimic their natural environment in lakes, the temperature of the water should be lukewarm to cool.

Marimo Moss Ball jar

When you change the water, about every two weeks, take out the balls and give them a gentle squeeze in a sink or bucket. Clean out the container and refill with lukewarm water.  You can then put them back in the water.

What is the best container for Moss Balls?

You will be happy to hear there a zillion types of containers that will work for your new plant.  I would recommend using a glass sided container so that the moss balls can get light through to the plant.  I use these simple glass jars with wooden tops from West Elm, but here is something similar.

I recently found this GORGEOUS round glass vase as well as terrarium kit and this glass vase with cork top.

Do Marimo Moss Balls need light?

Keep your moss balls where they will receive low to medium indirect light. You need to protect them from direct sun. Marimo balls can turn brown if they are getting direct light.  Marimo do well to even low light spaces like near a normal household light.

Moss Balls Care Tips

How often do I change the water for Marimo Balls:

It is best to change out water once every two weeks using regular tap water. You’ll need to change the water more often in summer, as it will heat and evaporate more quickly. Clean your marimo container with a brush if algae begins to grow on the surface.

Why are my Marimo Balls Floating?

Often times, after you clean our your container and place the moss balls back into the water… they will float along the top of the water.  That normally means there is an air bubble trapped inside that is causing them to float.  Simple squeeze your moss balls to “pop” the air bubble.  They will typically sink to the bottom of their tank within 1-2 days of being added back into the water.

Marimo Moss Balls, Care Tips, Light Needs

Shop all supplies needed for these amazing plants:

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