Marimo Moss Ball

About

Found across shallow lakes in the Northern Hemisphere, the marimo moss ball (Aegagropila linnaei) is one of the rare algae species that hobbyists actively seek out rather than battle against. It is not a true plant but a dense, velvety sphere of filamentous green algae, shaped over time by the gentle rolling action of lake currents and wave movement. In the wild these balls tumble slowly along the lake floor, staying round thanks to consistent water motion. In an aquarium you will need to rotate them occasionally to prevent them flattening on one side. They stay small and grow slowly, which suits a foreground placement well and means they will not take over a tank. Under low light they remain tidy and deep green, and they do not shed debris the way most algae would. If you want more of them, simply pull one apart into smaller chunks. Each piece will gradually round itself out over weeks or months, or you can press fragments flat against driftwood and rocks to create a soft carpet effect. They are notably protected in parts of Japan, where large natural colonies in certain lakes are considered a natural treasure. For a beginner wanting a low-fuss, genuinely unusual display piece, these are hard to beat.