Do Moss Balls Reduce Nitrates? Here’s What You Should Know

Marimo moss balls are often lauded for their ability to improve water quality. One key benefit is their ability to reduce nitrates in water, which are typically the byproducts of fish waste, uneaten food, and decaying organic matter. But how exactly do moss balls accomplish this, and how effective are they in reducing nitrates in a jar environment? Let’s learn the science behind it.

Key Takeaways:

• Moss balls reduce nitrates through photosynthesis by absorbing nitrates from the water.
• They’re most effective in smaller, low-maintenance setups (such as jars).
• Moss balls compete with algae for nutrients, helping to control algae growth.
• They should be seen as a supplementary tool, not a replacement for regular water changes or filtration.
• To maximize their effectiveness, ensure they receive consistent light and gentle water movement.
• The Science Behind Moss Balls and Nitrate Reduction

Moss balls reduce nitrates primarily through photosynthesis, where they absorb carbon dioxide and nitrates from the water. This process converts these nutrients into plant material while releasing oxygen. As a result, moss balls help improve water quality by removing excess nitrates, a common pollutant that can lead to poor water conditions and algae blooms.

Nitrates typically accumulate in water as a byproduct of organic decay. When left unchecked, they can contribute to algae overgrowth, low oxygen levels, and an overall decline in water quality. Moss balls help mitigate this issue by naturally absorbing these compounds and making the water cleaner and healthier for the entire system.

How Effective Are Moss Balls in Reducing Nitrates?

Moss balls are an excellent, natural way to help reduce nitrates and improve water quality in jars with gemstones. Their effectiveness depends on a few factors:

Size of the jar

Smaller jars (Moss Ninos) will see more noticeable benefits from moss balls’ nitrate absorption.

Amount of organic waste

If there’s excess organic material (such as dust, debris, or other waste), moss balls may need to be supplemented with regular water changes or cleaning to maintain optimal conditions.

Number of moss balls

Larger setups or jars (like Mega Moss) with more decorations may require more moss balls to help reduce nitrate levels effectively.

In low-maintenance setups with minimal waste, moss balls can have a significant effect on reducing nitrates. However, for environments with more organic buildup, moss balls should be viewed as a supportive element, not the sole solution.

Optimizing Nitrate Reduction with Moss Balls

To make the most of your moss balls' ability to reduce nitrates, follow these simple tips:

• Provide adequate light: Moss balls need indirect light for photosynthesis to occur. Ensure they get enough light per day (preferably indirect) to help them thrive.
• Ensure water movement: While moss balls don’t circulate water, gentle water movement can help them absorb nutrients more effectively.
• Regular water changes: Moss balls are a great supplemental tool for nitrate reduction, but regular water changes remain essential to maintaining a healthy environment.

Additional Benefits of Moss Balls Beyond Nitrate Reduction

In addition to helping reduce nitrates, moss balls offer a variety of other benefits to the water ecosystem:

• Absorbing excess nutrients: Moss balls help absorb other nutrients like phosphates, preventing nutrient buildup and reducing the risk of unwanted algae growth.
• Competing with algae: By taking up nutrients, moss balls naturally limit the growth of algae, helping maintain a clearer and healthier environment.
• Supporting water clarity: As moss balls absorb excess nutrients, they also help maintain biological balance, improving the overall clarity and quality of the water.

The Bottom Line

Moss balls are a low-maintenance and effective way to help reduce nitrates and improve water quality, especially in jars and smaller setups. While they shouldn’t be relied upon as the sole solution for nitrate control, they can still play a valuable role in maintaining a cleaner, healthier environment.

For more tips on caring for moss balls and getting the most out of their benefits, check out our Marimo Moss Ball Facts.

References:

What is nitrate? | US EPA. (2025, March 10). US EPA. https://www.epa.gov/mn/what-nitrate

The Editors of Encyclopaedia Britannica. (2025, May 7). Phosphate | Fertilizer, Agriculture, soil. Encyclopedia Britannica. https://www.britannica.com/science/phosphate