The Marimo Moss Ball (Aegagropila linnaei) is a popular aquatic accent, but it is not a moss. It is a rare spherical growth form of filamentous green algae. Its velvety texture and low-maintenance needs make it a sought-after addition to small aquatic environments. Understanding its unique biology and necessary precautions is important for the longevity of the algae and the protection of local ecosystems.
The Unique Biology of Marimo Moss Balls
Aegagropila linnaei consists of densely packed algae filaments that radiate outward from the center, lacking an internal core or seed. This structure allows the entire sphere to photosynthesize, provided all sides receive light exposure over time. In its natural habitat, the spherical shape is maintained by the gentle currents and wave action of lakes, which constantly tumble the algae.
This algae is exceptionally slow-growing, increasing in diameter by only 9 to 12.6 millimeters each year. In the wild, they thrive in cold, clean water environments and can reach lifespans exceeding 100 years. In an aquarium, the Marimo Moss Ball acts as a small biological filter by absorbing compounds like nitrates and ammonia. They also release oxygen during photosynthesis, contributing to the health of the aquatic environment.
Identifying and Mitigating Invasive Species Risk
The primary hazard when purchasing Marimo Moss Balls is contamination by the invasive Zebra Mussel (Dreissena polymorpha). These small, striped bivalves attach to the algae filaments and pose a severe threat if introduced into natural waterways. Zebra Mussels reproduce rapidly, causing significant ecological and economic damage by clogging water intake pipes and disrupting native food webs.
If you observe small, dark, or striped shells attached to your moss ball, immediately isolate it and contact your local natural resource agency. Do not dispose of the moss ball or aquarium water down any drain or toilet, as this creates a direct pathway to local ecosystems. Immediate destruction of the invasive organism is required before safe disposal.
There are three approved methods to destroy any potential contaminants before disposal. Following any of these methods, the moss ball must be sealed in a plastic bag and disposed of in the household trash.
- Freeze the moss ball in a sealed plastic bag for a minimum of 24 hours.
- Place the moss ball in boiling water for at least one full minute.
- Soak the algae in undiluted white vinegar for 20 minutes.
- Soak the algae in a diluted solution of unscented household bleach (one-third cup per gallon of water) for 10 minutes.
Safe Handling and Long-Term Care
Upon bringing a new Marimo Moss Ball home, a temporary quarantine period is recommended. Place the algae in a separate, clean container with dechlorinated water for at least one week, observing it for any changes before introducing it to an established aquarium.
For routine maintenance, change the water every one to two weeks using room-temperature, dechlorinated water. Gently rinse the Marimo Moss Ball and roll it between your palms during water changes to help maintain its spherical shape and ensure light exposure. These algae prefer low to moderate indirect light and should be kept away from direct sunlight, which can cause browning or overheating.
If you need to dispose of a Marimo Moss Ball, even a healthy one, the destruction methods (boiling, freezing, or chemical soak) must be followed to kill any potential organisms. Any liquid used for soaking or decontamination should be poured down a household sink or toilet, leading to a wastewater treatment facility. It must never be dumped into a storm drain or released into a natural body of water.