Marimo

Marimo is a growth form of the filamentous green alga Aegagropila linnaei, also sold under older Cladophora names. It is not a moss or a rooted flowering aquarium plant. The alga can occur in rounded colonies as well as attached or spreading growth, so the shape of a purchased ball is not the only indication of its health.

Growth is very slow. Keep water at 15 to 24 °C and pH 6 to 8.5, with a light range from low to high. This favours considering it for a cool aquarium, but does not establish that every ball must disintegrate as soon as the water exceeds 25 °C. Choose a suitable position and observe its condition rather than treating low light and cool water as the only inputs it needs.

Place the colony where it can be inspected and where debris will not accumulate unnoticed. During routine maintenance, check the surface and underside for trapped waste or deteriorating areas. Propagation is by separating portions of the algal growth; rebuilding a rounded colony is a slow process rather than an immediate result of cutting a ball. It offers a different texture from vascular plants, but is a poor choice if the goal is rapid growth or a quickly filled foreground.