A Curious Plant Pet: The Marimo Moss Ball

If you are looking for a new adorable plant to add to your collection, consider one of our favorites: the Marimo moss ball. 

The Marimo—meaning “seaweed ball” in Japanese—is actually not moss at all, but a rare species of algae that grows in fluffy, circular clumps. These velvety spheres can only be found naturally across a few lakes in the Northern Hemisphere and are known to live up to two hundred years. Marimo balls are slow-growing, expanding outwards at just 5mm every year, but can eventually grow to be the size of a basketball. 

In Japan, the Marimo moss ball is considered a national treasure. Lake Akan, which houses a significant number of Marimos, is an official Japanese national park, and Marimos have been deemed a protected species since 1920. In Hokkaido, the indigenous Ainu people host a three-day festival every October to honor them. 

According to Japanese folklore, the Marimo ball is a symbol of love and prosperity. Legend has it that there were two lovers who desired nothing more than to be together, but their love was forbidden. They fell into the waters of a lake, and their hearts transformed into Marimo balls. It is said that owning Marimo balls can bring your heart’s desire to both giver and receiver. 

Unfortunately, during the late 1990s, scientists noticed that Marimo moss balls began to decline in number due to human activities. Agricultural runoff has contaminated lakes home to large populations of Marimos, causing the species to rapidly deplete and become endangered. Today, Marimos can only be found in half the lakes where they were once identified. Controlling contamination will be critical for conserving the few remaining natural colonies of Marimos and reintroducing them to other countries. 

If you would like to own your own Marimo moss ball, caring for them is a simple task. Since they naturally form at lake bottoms, they require minimal, indirect sunlight. Good news – you also don’t need to worry about forgetting to water them! Keep your Marimo pets submerged in cool water, and change the water every 1-2 weeks. Your Marimos might also need a little help to keep their spunky round shape, and you can do this by gently squeezing them, rolling them around in your hands, or tousling the water inside their container to mimic natural waves. Have fun caring for these unique and beautiful plants! 


Written By Taiya Tkachuk



“Marimo Moss Ball Care: How to Grow and Care For Marimo Moss.” Pistils Nursery, 2 Feb. 2015, pistilsnursery.com/blogs/journal/marimo-moss-ball-care.

Roperch, Aurélie. “Ainu Legends and Marimo Algae on the Shores of Lake Akan.” Nippon100, 26 Jan. 2017, nippon100.com/en/akan-ainu-marimo.

Thorne, Egan. “Plant Profile: Marimo.” STUMP, 18 June 2018, stumpplants.com/journal/2018/6/18/plant-profile-marimo.

“Why Do ‘Japanese Moss Balls’ Float By Day And Sink By Night?” Forbes, 29 Aug. 2018, http://www.forbes.com/sites/grrlscientist/2018/08/29/why-do-japanese-moss-balls-float-by-day-and-sink-by-night/#7cbe3c644886

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