Light Requirements: Prefers low to moderate indirect light. Avoid direct sunlight, which can cause the ball to yellow or brown and promote algae growth. Artificial light is sufficient, especially in aquariums or jars.
Watering Needs: Change the water every 1–2 weeks using cool, dechlorinated tap water or aquarium water. In warm weather or bright conditions, change water more frequently to prevent overheating or fouling. Marimo should be gently squeezed during water changes to release trapped debris and oxygen.
Soil Preference: No soil is needed. Marimo balls float or sit loosely in water and can be placed directly in aquariums, bowls, or jars. Gravel or sand can be used for aesthetic purposes, but it’s optional.
How to Fertilize: Generally does not require fertilization. In aquariums, it may benefit from trace nutrients already present. In nutrient-poor setups, a tiny amount of aquarium plant fertilizer can be added monthly if growth slows.
Hardiness Zone: Best kept indoors in a controlled water environment. It prefers temperatures between 50–77°F (10–25°C). Avoid placing it in hot water or letting temperatures rise above 78°F (26°C), as this can cause stress or decay.
Pet Safety: Non-toxic to cats, dogs, and fish. Marimo is safe in aquariums and pet-accessible containers, though curious pets may try to play with it.
Additional Care Tips: Roll the Marimo gently in your hands during water changes to help it maintain a round shape and prevent flat spots. Rinse lightly if it becomes slimy or coated with debris. It grows very slowly—only about 5 mm per year—and can live for decades. Can be split into smaller balls if desired. If it floats, it may be holding air bubbles and should be gently squeezed and rotated underwater.
