What is Marimo and how is it treated?

Marimo seaweed ball

Marimo was discovered in 1820 in Japan. This alga also known as Cladophora ball, moss ball, or lake ball, is a rare form of Aegagropila. The shape of the Marimo is usually spherical, green in color and velvety in appearance.

What does the name Marimo mean?

The name marimo was given by the Japanese botanist Tatsuhiko Kawakami in 1898.
Mari means marble and Mo is a generic term for plants that grow in water.
The best known shape is the spherical one (egagropili) , due to a cluster of stems that develop radially from a free "tuft" in the water.
The movement of the water allows the algae to acquire a spherical shape, guaranteeing all the stems sufficient oxygenation and lighting.
During the day the spheres float on the surface of the water as photosynthesis produces oxygen which drags the sphere towards the surface.

Where are Marimo found in nature?

Marimo's preferred habitat is in shallow lakes with low or moderate biological activity and moderate or high calcium levels.
It can develop on the muddy bottom of lakes, forming a compact horizontal carpet, or it can cover submerged rocks and wood.
This marimo species can be found in numerous lakes and rivers in Iceland, Japan and from Siberia to Estonia , while they have been introduced by man to Australia . They were also found on the Costa Verde of Sardinia , after a great storm.

Curiosities about Marimo

Numerous oxygen bubbles will be visible to your eyes on the mantle of the Marimo.
Scientific studies have shown that marimos absorb a large amount of nitrites, nitrates and ammonium components in the water, releasing a large amount of oxygen forming so many bubbles visible on the stems of the marimo.
Marimo loves water but sparkling water even more. If you want to see them dance, add two fingers of sparkling water to the jar, this will allow it to have more carbon dioxide to transform, so you will see it in motion!

How to take care of the Marimo?

  • Irrigation: change the water every 10 days;
  • Temperature: it must not exceed 23 degrees;
  • Exposure: do not expose it to direct sun and it is not afraid of the dark;
  • Maintenance: if it is green it is fine, if it becomes yellow / gray it is in pain.


It is important to change the water every 10 days .
The water is emptied, squeezed, the jar rinsed, fresh water added, swirled in the palm of the hand and the Marimo plunged back into it. Tap water or bottled water can be used. Occasionally (or always) it is fun to add sparkling water so that the Marimo can transform carbon dioxide into oxygen.
The Marimo needs the change of water to be able to consume the mineral salts. If the water is not changed, the Marimo is stationary in its growth. The more you change the water, the more the Marimo will grow. If you go on vacation for a long time and don't change the water, nothing happens.


The ambient temperature should not exceed 23 degrees. Beyond this temperature, the ideal is to take it to the refrigerator! Place the Marimo inside the refrigerator in the summer, remembering to keep the water change every 10 days and not to eat it!

Solar exposure

It does not need particular light because it is used to living on the bottom of lakes, but be careful, it should not be exposed to direct sunlight!


It is important to keep an eye on its color. If the Marimo is green it means that it is fine , if it is yellow / gray then it has taken a hit of heat and is probably in pain.
Anything that can cause the water temperature to rise can damage it and surely cause it to die.
Pay attention to the temperatures and do not place it near the heater.
The important thing is to keep it in an always cool place.

As well as keeping you company, Marimo is beautiful and can be an excellent gift idea!

You can find them in our Garden Center in the Indoor Plants department or you can buy them directly from here:

Marimo seaweed 2-3 cm ball


Marimo seaweed 3-4 cm ball


Marimo alga ball 5-6 cm