Marimo Moss Care Guide
Struggling to keep your Marimo moss balls alive?
This simple guide shows you exactly how to care for them and keep them healthy, green and thriving.
Marimo moss balls are actually a type of freshwater algae, but they are incredibly easy to care for once you understand the basics. With the right water, light and occasional cleaning, they can live for years and continue to grow slowly over time.
At Highland Moss, we work with Marimo regularly, so this guide is based on real experience and practical care. All Marimo from Highland Moss come with beautifully illustrated care guides, making them easy to look after for beginners and experienced plant lovers alike.
Marimo moss balls are easy to care for once you understand the basics.
All Marimo from Highland Moss come with beautifully illustrated care guides to help you keep them healthy with confidence.
Marimo are one of the easiest aquatic plants to care for and can live for years with very little effort.
About Marimo moss balls
Despite the name, Marimo moss balls are not actually moss. They are a rare form of filamentous green algae called Aegagropila linnaei. They are also sometimes known as lake balls or Cladophora balls.
In the wild, Marimo grow underwater in cold freshwater lakes in places such as Japan and Northern Europe. Their round shape develops as they gently roll along the lakebed with the movement of the water. This rolling action helps them stay compact and evenly shaped.
Marimo are loved for their unusual look, easy care, and quirky charm. They make a great first plant, a low maintenance gift, or an interesting addition to a desk, shelf, or aquarium.
Care Instructions
Marimos are very easy to look after. They are perfect as a first household plant, for busy plant parents and they make a quirky and unique gift.
Light
Marimo prefer low to medium indirect light. Try to recreate their natural habitat, which is the cool, darker bottom of a lake.
Avoid direct sunlight, as this can cause your Marimo to become pale, develop brown patches, or lose its healthy green colour.
Water
Marimo should always be kept underwater. Change the water every 2 to 3 weeks using cool, clean water. In warmer weather, you may need to top up the water more often as it can evaporate more quickly.
Tap water is usually safe to use, although filtered water can help keep Marimo cleaner for longer.
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Sparkling water boost
Sparkling water can occasionally be used to give Marimo a little boost, as the added carbon dioxide can support photosynthesis.
You can either:
-Give your Marimo a short sparkling water bath after cleaning the container, then replace it with normal water the next day
-Mix 1 part sparkling water with 2 to 3 parts normal water once a month
This is optional, but many people find it helps keep their Marimo looking fresh.
Keeping Marimo round
In nature, water currents gently roll Marimo along the lakebed, helping them keep their round shape. In a container, they do not get this movement, so over time they may start to flatten.
To help them stay round, gently roll them between your hands from time to time or lightly move the water in the container.
Fresh air
Open your Marimo container regularly to let in fresh air. This can help keep the water fresher and support healthy growth.
Are Marimo safe for pets?
Yes, Marimo moss balls are considered non-toxic to humans and pets. Marimo moss balls are perfect for fishtanks!
Pests and unwanted visitors
Pests are uncommon in Marimo kept indoors. However, if you use rainwater, make sure it has been stored properly, as poor storage conditions may introduce unwanted hitchhikers such as mosquito larvae.
Sometimes unwanted algae can also grow on the outside of your Marimo. If this happens, rinse it well and gently remove any visible algae. In many cases, Marimo can naturally compete with nuisance algae by using the same nutrients.
What should a healthy Marimo look like?
A healthy Marimo should be bright green and feel firm yet soft to the touch. They are not naturally perfectly round, so uneven or slightly misshapen Marimo can still be completely healthy.
Why is my Marimo floating?
Floating is completely normal. During photosynthesis, small oxygen bubbles can build up inside the Marimo, causing it to rise to the surface.
You can leave it and it will usually sink again on its own. If you want to help it sink faster, gently squeeze it underwater to release the trapped air.
Marimo Moss Balls Common Issues
Pale or white colour
Pale or white colour is often caused by light that is too strong, so move your Marimo to a more sheltered spot with lower light. It can also happen if the Marimo has dried out. If it has not been left without water for too long, it can often be saved by placing it back underwater and allowing it time to rehydrate.
Brown or black spots
If the brown marks do not wash away, the issue is often lighting related. Browning can happen if the Marimo is getting too much direct light, but if the marks are mainly underneath, it may also need a little more gentle indirect light. Trim damaged area with sharp scissors and reduce amount of light to fix the issue.
Zebra mussels
In rare cases, Marimo moss balls can be linked to zebra mussels, an invasive species. If you would like to understand this issue in more detail, you can learn more about zebra mussels and Marimo in our article. Click here to read the article about zebra mussels.
Marimo care basics
Marimo moss balls are easy to care for. Keep them in clean, cool water with low to medium indirect light. Change the water every 1 to 2 weeks and gently roll them to maintain their shape.
Can you save a damaged Marimo moss ball?
Yes – Marimo are very resilient and often recover well with a little care. A gentle trim, rinse, and rolling between your hands can help improve their shape and colour. If you would like to rescue one and save money, view our imperfect Marimo options – a great value choice for aquariums and other aquatic setups.
