Marimo Moss Balls are algae balls (although they are referred to as moss balls due to their visual look). They are interesting decoration suitable for smaller aquariums. They are also available in larger sizes and in nature reach up to 20-30 cm. They are not demanding in terms of conditions, but they do better with medium light. Together with stones and roots, you can achieve an attractive aquarium design.
Interestingly, this algae usually forms carpet surfaces at the bottom of lakes in Japan and Northern Europe, but if a piece of it separates, it is carried away by waves, which eventually make it a ball. Even in the aquarium, it is good to turn them from time to time to maintain their shape. When they grow to a certain size, they can be split.
They grow at a rate of 0.5cm per year and are often used in shrimp tanks and are useful to control the growth of unwanted algae as they compete for the same food source.