Marimo Moss Ball

Marimo (Aegagropila linnaei) is not a true moss but a rare form of filamentous green algae that naturally grows into a ball shape by being rolled along lake bottoms. It is one of the slowest-growing aquarium plants, adding only a few millimetres per year under ideal conditions. Marimo absorbs small amounts of ammonia and nitrates, providing minor biological filtration, and is extremely long-lived — specimens in the wild can live for centuries.

Light: low light; avoid direct intense light which causes browning. CO2: not required; absorbs CO2 directly from water. Placement: place on substrate or attach to a small stone; rotate weekly to ensure even light exposure. Maintenance: gently squeeze and rinse in tank water monthly to remove trapped debris and refresh the interior. Growth: very slow; propagate by splitting larger balls into halves and rolling into shape.