Do Moss Balls Oxygenate Water? Here’s What Actually Happens

Moss balls do oxygenate water, but only under the right conditions, and the impact is modest. They release oxygen during daylight hours through photosynthesis, just like other live aquatic plants. That said, their contribution is usually not enough on its own to maintain healthy oxygen levels in most setups.

Key Takeaways:

• Moss balls produce oxygen, but only when exposed to light.
• Oxygen output is minimal, and not enough to support closed systems on its own.
• They can help with nutrient absorption and support biological balance.
• They don’t circulate water, so they can’t replace mechanical aeration.
• Best used as a supporting element, not a primary oxygenation solution.

How Moss Balls Contribute to Oxygen Levels

These algae spheres use photosynthesis to absorb carbon dioxide and release oxygen back into the water. This only happens when they’re exposed to light. In the dark, the process stops, and oxygen levels can actually dip slightly due to their natural respiration.

As noted in the study The phytobenthic zone, Aegagropila linnaei (Marimo moss balls) contributes to oxygenation through photosynthesis, especially in environments where light exposure and other growth conditions are favorable. However, their contribution to oxygen levels remains modest compared to larger, faster-growing plants.

Photo by Beckett L., Moss Amigos Internship

But unlike high-growth aquatic plants, moss balls are extremely slow-growing. That means their oxygen output is relatively limited.

If the goal is to increase oxygen levels in a closed-water system, moss balls might help a bit, but they won’t replace mechanical or biological solutions that promote active water flow and surface agitation.

How to Boost Their Oxygen Output

To get the most out of moss balls, light exposure is critical. They don’t need intense light, but they do need consistency.

Here’s how to support photosynthesis:

• Place near a window with indirect natural light or use soft artificial light for 8–10 hours per day
• Avoid blocking them under decorations or other items
• Rotate occasionally so all sides receive light
• Maintain stable water temperatures (68–77°F or 20–25°C)

The more light they get, the more consistently they contribute oxygen.

Must Read: How much light does a moss ball need?

Can Moss Balls Oxygenate Water Without Other Help?

Not effectively. Moss balls don’t move water or increase surface exchange. That’s where real oxygen transfer happens at the surface, especially when water is agitated.

If you’re relying only on passive oxygenation, and the water is still, moss balls won’t be enough. They're best used in combination with other oxygenation methods or in setups with low biological demand.

Do Moss Balls Help Improve Water Quality?

Yes, and this is where they shine more clearly. Aside from light oxygen production, they help:

• Absorb excess nitrates and phosphates
• Reduce build-up of organic debris
• Offer surface area for beneficial microbes
• Compete with algae for nutrients, helping limit outbreaks

This combination of biological activity indirectly supports water clarity and stability, which benefits oxygen levels overall.

Where to Place Moss Amigos for Optimal Oxygenation

If you have your Moss Amigos in a jar, make sure they get plenty of indirect light throughout the day. This helps them perform photosynthesis, which is key to producing oxygen. Since they’re in a jar, the water doesn’t circulate much, so changing the water regularly is important to keep it clean. 

A simple setup like this can help your moss balls absorb excess nutrients and maintain a balanced environment, but don’t forget, they’ll still need a bit of TLC to stay healthy!

The Bottom Line on Moss Balls Oxygenating Water

Moss balls do release oxygen, but their impact is limited and only occurs during light periods. While they’re a great addition to stable, low-demand setups, they can’t fully replace more active oxygenation methods. 

They help maintain water balance, absorb excess nutrients, and support the microbial ecosystem, making them a valuable, supplementary tool, but not a primary solution for oxygenation needs.

To learn more about moss balls and how to care for them, check out our Marimo Moss Ball Facts.

References:

Kautsky, H., Martin, G., & Snoeijs-Leijonmalm, P. (2017). The phytobenthic zone. In Springer eBooks (pp. 387–455). https://doi.org/10.1007/978-94-007-0668-2_11

Nakayama, K., Komai, K., Amano, M., Horii, S., Somiya, Y., Kumamoto, E., & Oyama, Y. (2023). Ideal water temperature environment for giant Marimo (Aegagropila linnaei) in Lake Akan, Japan. Scientific Reports, 13(1). https://doi.org/10.1038/s41598-023-43792-6

https://www.cell.com/current-biology/fulltext/S0960-9822(18)30926-6