Watering requirements
Keep submerged in distilled or filtered cold water. Change water once every 1-2 weeks, depending on algae growth. If your Marimo is floating on the water's surface and/or creating bubbles, it is producing oxygen! This is natural.
Fun Fact
The marimo 'moss' ball as it is commonly known is not actually moss at all, but a freshwater, filamentous green algae colony.