Marimo FAQ

Posted by Sacred Elements on

"I love your tutorials and have now brought my sweet Marimo back to life. Thank you so much!" —Stephanie T.

We get a lot of questions about our favorite little floating balls of love: Marimo. Here’s a quick list of our most frequently asked - hope it helps! Contact us at if you need help or have a specific question that wasn’t answered.
Handful of Love.What’s the history of Marimo? 

The history of Marimo can be traced back to a few freshwater lakes around Europe and Japan. The most well known is Lake Akan, Japan where up to 6,000,000 Marimo grow slowly in the cold, bowl-shaped freshwater lake. Marimo were first discovered in 1820 by Anton E. Sauter, who happened upon the curious green balls in Lake Zell, Austria. Later,  Japanese botanist Tatsuhiko Kawakami in 1898, deemed them Marimo, ‘Mari’ meaning ball and ‘Mo’ meaning seaweed, algae or aquatic plant. 

Many of you have probably heard of the folklore around Marimo: two lovers, unable to be united, she the daughter of a chief and he a commoner, run away together but fall into Lake Akan and drown, their hearts becoming the first Marimo. Sweet, tragic and definitely memorable! Today, in Japan and now all over the world, Marimo are given as a token of love, and offered as a gift for your heart’s deepest desire. 

Are Marimo endangered? Are they sustainable?

 In 1921 Marimo were designated a National Treasure in Japan. However, as Lake Akan and the surrounding area began to develop, the number of people wishing to possess this strangely beautiful algae increased too. Despite their new classification as a protected species, their numbers dwindled as a result of illegal harvesting, the people of Lake Akan looked for ways to protect Marimo against extinction. And in 1950 the first Marimo Festival was conceived to inspire people to actively protect and honor the endangered algae of Lake Akan.

Today, Marimo are grown sustainably in farms across Japan and throughout Eastern Europe. The Marimo we curated and sell in our shop are grown and harvested from a responsible source with the utmost care and attention to the environment. We want to keep Marimo happily thriving and untouched in their natural, protected habitat too! We only source from one trusted supplier so we can continue to encourage people to bring them into their homes to grow, educate and inspire natural world connection

Are Marimo a good choice for beginners?


Marimo is an excellent choice for beginning houseplant enthusiasts and long time plant parents alike. Since marimo need very little attention, they are perfect for kids who want their very own 'houseplant', a wonderful gift for newlyweds as they are a symbol of love, and a thoughtful heirloom that can be passed down from generation to generation. 

How do I keep the Marimo?

We recommend housing your Marimo in an open, glass vessel. You may add cleaned and rinsed rocks, crystals, shells, other aquatic plants and fish to the vessel (care tips are different once you add a fish). For those of you who have a curious cat & need to put a lid on your Marimo, we recommend one that breathes for optimal air circulation. Consider the natural environment of Marimo, lakes don’t have lids! 

How often should I clean my Marimo? 

We like to clean the Marimo vessel and Marimo every 10-14 days, but they can easily go longer, up to three-four weeks if need be. To wash the Marimo, gently remove from the vessel and squeeze each Marimo gently, slowly, and firmly (like a hug) with two cupped hands to avoid tearing, then roll hands together in a circular motion to reshape. To clean the vessel and rocks, shells or crystals, dump out old water, rinse and wipe down surfaces with a clean sponge or cloth, be mindful of soap residue,  just use water with the scrubbing motion to clean and then rinse thoroughly. Maybe have a dedicated sponge just for Marimo! Refill vessel with cold tap/distilled water and add a dash of Marimo Salt. Gently clean, rinse & replace rocks or decorative crystals along with Marimo and place in indirect light to display. We recommend using a lightly dampened cloth with a dash of vinegar to clean the outside and inside of the glass vessel to keep the surface looking bright and clean without smudges or older water line marks. 

Troubleshooting Marimo Issues:

White spots can be caused from two things, either too much exposure to light or a hostile algae has decided to attack.

If the white spots are on the end of the green "hairs" and look bleached out, then you are dealing with too much light. Your Marimo are just a bit burned and need to be moved to a new location. Go ahead and gently trim off the burned filament with clean, sharp scissors (I use cosmetic scissors) and clean as instructed above.

If the white spots are harder and attached to the actual ball then you are dealing with a hostile algae and we need to cut away or use tweezers to gently pull off all the white color before giving your Marimo a saltwater bath as instructed below. Be sure to clean the vase or container well with either a drop of bleach and hot water, or vinegar and hot water, rinse well and replace with clean tap, spring or rain water before adding Marimo back to their home. 


Bonus Tips:

    • During the warmer months you can add a handful of ice cubes or pop the entire vessel into the refrigerator for a few days to give Marimo a little vacation! 

    • We recommend adding carbonated water 1-2 parts carbonated water to tap, rain or spring water, once every month or so. The CO2 boosts photosynthesis and is so fun to watch teeny tiny bubbles collect along the surface of the Marimo as it photosynthesizes! 

    • Adding a pinch of Marimo Salt to their water helps prevent any grey or brown spotting while also reducing biofilm (a slimy film that floats in and on top of the water) while keeping them feeling right at home. If biofilm continues to float on top of the water you can try this too!

    • Remove Marimo and clean vase or vessel with hot water and vinegar and rinse well making sure to cool off the vase before adding fresh, cold water again. Then, give Marimo a full ocean soak by following our instructions here:

  • add 7 teaspoons of our Marimo Salt  to a liter of water and mix well until fully dissolved. Place Marimo in salt water solution, out of any direct sunlight, and let sit for 24-36 hours. Remove and rinse under cold tap water for 10 seconds, squeezing gently before replacing them into spring, rain or tap water once again.

How long can Marimo live?

In their natural habitat, marimo have been documented to live up to 200 years.

They grow slowly (approximately 5 millimeters a year) and the largest marimo found to date is roughly the size of a basketball!

Can you put other plants or animals in with Marimo?

Adding other plants or animals to your Marimo is no problem. If you’d like to build your own indoor water garden and include Marimo for their amazing shape and texture-go for it! If you want to give your freshwater fish a few green friends to keep them company and help them feel safe, no problem. Just be sure to follow all instructions for proper fish care and clean your Marimo as suggested above.

Why do they float or sink?

In their natural environment, when marimo photosynthesize, they produce oxygen making them buoyant & keeping them closer to the surface of the water. When the light fades, marimo no longer photosynthesize and they descend once again to hang out at the bottom of the lake. The second reason marimo float is due to their circadian rhythm. We cover these concepts in our new downloadable lesson plan Volume 1-3 of Sacred Elements Plant School. Their unique round shape keep marimo photosynthesizing no matter how they roll which is vital to keeping them from getting sunburnt. 

Marimo need movement! Give your marimo vessel a little swirling action every so often to keep them moving and feeling like they’re right at home among the soft lake currents.

Each ball is formed as long strings of algae filament roll along the bottom of sandy lakes and bind together along the shallows of these waters. Their average size is about that of a golf ball, but some  grow much larger as they age. 

They propagate by ‘budding’ or forming a new little version of themself that will eventually tear away and become its own marimo.

Why are Marimo different shades of green?

Coloration depends on lighting over time. Darker green is more common and a sign of optimal health. Lighter green is likely due to more lighting exposure over time, but doesn't necessarily mean there is a health issue. 

Why do some Marimo have fuzzy, short 'hair' and some have longer?

There is only one species of 'real' Marimo, with 3 types of growth forms:

  1. ‘Epiphytic’ marimo that grow on the shaded side of rocks
  2. ‘Free-floating’ filaments that form a carpet on the surface of water
  3. ‘Spherical’ marimo are orb shaped made up of thousands of strands of densely packed algal filament.

If you find you have a Marimo with “short hair” which tend to be more fuzzy, then you have a more rare version, but still the same type of green friend. There is no difference in species looking at the filaments under microscope, just subtitle variations. 


Want to learn more? Here is our most recent Youtube video

Why are we currently sold out of Marimo?

You may have heard the alarming news that an invasive, destructive species of freshwater mussels have been hitchhiking their way across the globe on Marimo. Zebra Mussels reproduce quickly and alter food webs by overconsumption of plankton. This in turn increases harmful algae overgrowth and wreaks havoc in waterways, causing an imbalance to our ecosystem.

Sacred Elements developed our relationship with our trusted supplier of Marimo years ago specifically and intentionally because of their conservation practices and attention to detail. They are in alignment with our goal of protecting our natural resources. Our beloved Marimo have been Zebra Mussel free for many proactive reasons they put into place years ago that we wanted to share with you here.

In addition, our team here at Sacred Elements sorts through each and every Marimo we receive. We then clean them extensively, individually inspecting them for health and vibrance. After that process we care for them in our small shop before carefully packaging and sending them out to you. That is why we tend to have wait times and preorder status on our website. We only send out healthy, thriving products so you can experience the wonder that is Marimo!

Read full zebra mussel blog post here 

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