Why Marimo Moss Balls Turn Brown: Causes and Solutions

Why Marimo Moss Balls Turn Brown: Causes and Solutions

Seeing your Marimo moss ball turn brown can be a surprise, especially when they're known for their vibrant green color. 

Yet, when they start showing signs of brown, it's a clue that something's not quite right.

Don't fret, though!

Understanding why this happens and how to help them can get your Marimo back to its lush green self. Let's explore the reasons behind the color change and explore simple solutions to keep your Marimo moss ball happy and healthy!

Wait, Why Are Marimo Moss Balls Green?

Marimo moss balls are green due to chlorophyll, a pigment responsible for the green color in plants. 

molecular structures of chlorophyll a and chlorophyll b

Chlorophyll is essential for photosynthesis, the process by which plants convert light energy into chemical energy to fuel their growth. 

Marimo balls are a type of algae, specifically a species called Aegagropila linnaei, which naturally produces chlorophyll. 

Now, Here’s The Main Cause

Marimo moss balls turn brown because they get too much light or are in too warm water. They like cooler places with less light. When it's too warm or bright, they lose their green color because the green stuff in them gets less. 

 Diagram comparing permafrost covered by snow and exposed to sunlight

Here are the two main cause solutions.

For Lighting:

Marimo balls require a balance of light to stay healthy. If they're kept in a room that's too dim, consider moving them to a spot with more indirect sunlight or use a gentle LED nature light to mimic natural conditions. 

Our cute Moss Amigo Hat is the perfect solution for those moments when you want to safely introduce your Moss Amigo to direct sunlight without the risk of overexposure. Recommended for less than an hour of playtime, it ensures your green buddy enjoys the sunshine in moderation, preventing browning due to a lack of photosynthesis, especially during the darker months.

For Water: 

Regularly changing your Marimo's water with dechlorinated or tap water is essential. If you've noticed the water getting cloudy or your Marimo browning, a freshwater change can help. Bi-weekly changes are recommended to keep the water clean. To simplify this process, consider our starter kit, which includes purified water perfectly suited for your Marimo, ensuring a healthy environment without the hassle of treating tap water.

You can also read this: Is Your Marimo Moss Ball Turning Yellow? Find Out Why!

You might be curious if there are additional reasons beyond what we've covered. Let's get deeper into other potential causes below.

  • Aging: Over time, like all living things, Marimo balls can show signs of aging, which includes browning in parts of their surface.

Tip: As Marimo moss balls age, some browning is natural. If your older Marimo shows signs of browning, carefully trimming away the affected areas with sterilized scissors can encourage fresh, green growth. 

  • Nutrient Imbalance: An imbalance in nutrients, whether a deficiency or an excess, can detrimentally affect their health, manifesting as poor growth and browning. It is crucial, as outlined by sources such as ScienceDirect, to avoid inadvertently introducing algaecide chemicals into your moss ball pet's environment, which can cause harm. 
  • Physical Damage: Rough handling or constant movement can bruise or damage the algae, causing brown spots to form.

Tip: Gentle handling is key. If you've been cleaning your Marimo by rolling it aggressively, this could cause physical stress, leading to browning. Instead, swish it gently in a bowl of dechlorinated water to clean it. This method ensures it stays intact and doesn't suffer from rough treatment. Consider using a moss handler to ensure gentle handling and protect your Marimo from damage. It's a beautiful, practical tool designed for the safety and care of your Moss ball.

Want to know more about Marimo moss balls? Check out our article, "8 Unexpected Facts About Marimo Moss Balls," to learn cool stuff today!


Seeing your Marimo moss ball turn brown can be disheartening, but it's often a fixable issue. By understanding the causes and implementing the suggested solutions, you can restore your Marimo to its lush green state. For more detailed guidance on preventing browning and keeping your Marimo moss balls vibrant and healthy, visit Moss Amigos. Thanks for reading!


Martin, C. E., & Churchill, S. P. (1982). Chlorophyll concentrations and a/b ratios in mosses collected from exposed and shaded habitats in Kansas. Journal of Bryology, 12(2), 297–304. https://doi.org/10.1179/jbr.1982.12.2.297

Ramirez, D. C., De Fraine, T. S., Griffiths, O. G., & Dodd, A. N. (2018). Photosynthesis and circadian rhythms regulate the buoyancy of marimo lake balls. Current Biology, 28(16), R869–R870. https://doi.org/10.1016/j.cub.2018.07.027

Nishida, G., Yoshimoto, M., Lens, J., & Kawano, S. (2013). A geometrical approach explains Lake Ball (Marimo) formations in the green alga, Aegagropila linnaei. Scientific Reports, 3, 3761. https://www.nature.com/articles/srep03761

Pokorny, K. (2015, March). Here's the scoop on chemical and organic fertilizers. Oregon State University Extension Service. Retrieved February 16, 2024, from https://extension.oregonstate.edu/news/heres-scoop-chemical-organic-fertilizers

Gupta, A., Saraswat, P., Yadav, K., Prasad, M., & Ranjan, R. (2021). Physiological and molecular basis for remediation of pesticides. In Elsevier eBooks (pp. 551–568). https://doi.org/10.1016/b978-0-12-819382-2.00035-1


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