Marimo Moss Balls(Aegagropila linnaei / Cladophora aegagropila)aren’t actually moss! They’re a rare, slow-growing algae that naturally forms into soft, velvety green spheres. In the wild, Marimo grows at the bottom of lakes in Japan, where water currents tumble the algae into its signature moss ball shape. The name Marimo directly translates to “seaweed ball” in Japanese, and it’s arguably the only algae species welcomed openly in freshwater aquariums.
Marimo Balls are very much alive and make a unique, moss-like addition to any freshwater aquarium or planted tank. They’re often used in low light tanks for greening, an aquascaping technique where moss is attached to driftwood and rocks to create an aged, natural look. Simply pull the ball apart and gently wedge into cracks or attach with a very small amount of adhesive. Marimo Balls are also decorative on their own and are often kept in glass jars or similar containers. They’re great for betta fish tanks, shrimp setups, and more. If your Marimo floats, it likely has air trapped inside. Squeeze it gently to release and drop it back in!
Quick and easy examples of the greening method and how to unball a Marimo Moss Ball:
How to care for a Marimo Ball
Marimo Balls require very little maintenance. They prefer cooler water temperatures below 76°F. In still water or under stronger lighting, you may need to manually rotate them occasionally to ensure all sides receive light. Otherwise, they’re fine in low light, tolerate a wide range of water parameters, and can even survive in slightly brackish water. Their hardy nature and minimal care makes them a top beginner “aquarium plant”!
| Common Name | Marimo Ball |
| Care | Easy |
| Lighting | Low to Medium |
| CO2 | Optional |
| Suggested Placement | Loose / Attached to hardscape |
| Propagation | Gently separate |
| Growth Rate | Varies |
| Height | Varies |
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