All About Marimo


Despite being known as Marimo moss balls, these quirky plants are a species of filamentous green algae. The scientific name of this algae is Aegagropila linnaei and lives in freshwater where it can occur attached or unattached. It is widely known for its unattached spherical growth form, also referred to as “Marimo,” “lake balls,” or “Cladophora balls”.

They can be found growing at the bottom of lakes and rivers in Japan and Northern Europe. This rolling moss was even featured in The Green Planet: Water Worlds featuring Sir David Attenborough.


The young Marimo rolls thanks to the currents formed in the lakes where they live. Using these currents, they need to find the perfect spot: away from predators (like swans) but not too deep in the lake, or else it would not receive enough sunlight.

They form colonies of thousands of Marimo moss balls.

Care Instructions

Marimos are very easy to look after. They are perfect as a first household plant, for busy plant parents and they make a quirky and unique gift.

Light Conditions

Your marimo should live in a spot with low to medium indirect light. Think about its natural habitat, we are trying to recreate the dark cold bottom of a lake. Direct sunlight will make your marimo start to turn pale or developing brown spots.


Marimo should live underwater and require occasional water change, ideally every 2-3 weeks with cold water. You might need to top up the water more often during summer as evaporation will occur more rapidly.

Tap water can be used safely, though they will remain cleaner longer in filtered water. 

Pro Tip

Your marimo moss balls would enjoy occasional use of sparkling water.

Sparkling water helps due to the added intake of CO2, which will provide your Marimo moss balls with a boost to assist the photosynthesis process. There are two ways you could do this:

  1. After removing the old water and cleaning your container, pour plain sparkling water. Add your wee Marimos and let them enjoy the bubbly bath. The following day, swap out the sparkling water for their conventional water (tap or distilled water).
  2. You can opt for once a month, mix sparkling water with normal tap water (or distilled water). An ideal ratio would be 1 part of sparkling water and 2 to 3 parts of normal water.

Staying in shape

In the wild, the water currents make the Marimos gently roll over the bottom of the lake, encouraging the algae formation to stay round.

As there is no movement in your Marimo reservoir, eventually they will tend to flat out. To prevent this, you can gently move the water of your Marimo enclosure or very carefully roll it softly between your hands.

Open the container with Marimo regularly to provide access to fresh air to keep them thriving. 


Pests are very rare in household Marimos. Nevertheless, be mindful if you use rainwater, as poor-storing conditions might carry hitchhiker like mosquito larvae.


Moss balls are not toxic to humans or pets.


This is completely normal and is due to your Marimo performing photosynthesis as part of their circadian rhythm. Small oxygen bubbles are formed and some of these get trapped inside your Marimo, causing it to float. You can leave it and it will eventually sink again, but otherwise you can give your Marimo a gentle squeeze to release the air.

Your healthy Marimo moss ball should look bright green.

  • Pale or white: the most likely issue is that you are providing light that is too harsh for your Marimo. Move it to a slightly more sheltered location and the colour should improve.
  • Brown spots: try cleaning them, if they do not disappear and are mostly at the bottom of you Marimo, the issue is insufficient light. 
  • White spots: There might be unwanted guests living in your Marimo. Give it a thorough clean and isolate from other Marimo moss balls until the issue has resolved.

Occasionally, hostile species of algae can grow on the surface of your Marimo. Give your Marimo a thorough wash to eliminate them or remove it carefully with tweezers. Nevertheless, Marimo moss balls will eat the same nutrients as undesirable algae, hindering their development.

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