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Last Updated:May 19, 2023

Marimo Moss Ball Care – The Only Guide You’ll Ever Need

featured-marimo moss ball care

In this Marimo Moss Ball care guide, besides temperature, light, propagation, and other care tips you will find out why they float, what type of water they like, or how long they live.

Botanical Name (Latin Name/Scientific Name): Aegagropila Linnaei
Common Name: Marimo Moss Ball
Light: low light tolerant (50 lux – 750+ lux)
Watering: refill the dish once a week and replace water every 2 weeks
Soil: no soil needed, it lives in water
Repotting: not needed, it lives in water
Temperature: 63°F to 73°F (17°C to 23°C)
Humidity: not applicable, as it lives in water
Toxicity for Pets: Non-toxic
Toxicity for Humans: Non-toxic
  • division
Pruning: trim them if certain parts turn brown, or if you want to split a moss ball

Light Requirements

Minimal amount of light: 50 lux (5 FC)
Optimal amount of light: 750+ lux (75+ FC)
Direct sun tolerance: 0 hours
Category: low light tolerant

Moss Balls’ light requirements are low. Marimo Moss Balls live at the bottom of cool lakes in their natural habitat. Thus, they don’t receive direct light (direct sunlight) nor a lot of indirect light in general. This is good news because it means that the average household light intensity is sufficient for Marimo Balls.

Water Needs

Marimo Balls live in water, that is clear. However, that raises a few questions. Is clean water important? If yes, what type of water should you use?

Let’s dive in (no pun intended) for more details.

Do I Need To change The Water?

Yes, you need to change the water. Clean water is important as, over time, different bacteria and fungi can multiply and decrease the water quality. The frequency isn’t set in stone, and it depends on many factors, but in general, you should change it once a week or every two weeks. Some of the factors that affect how often you would change it are:

  • Do you only have Marimo Moss Balls in your aquarium or not? If you only keep Moss Balls, then you usually need to change it approximately every two weeks. If, however, you also have some fish, you’ll probably need to do it more often to keep the water quality.
  • How hot is it in your flat? In summer or during very hot periods, the water evaporates more quickly so you’ll have to refill it more often.

What Type of Water Should I Use?

You can use regular tap water on your marimo. In fact, the same water you would use for your fish tank. You could treat the tap water with a water treatment solution which you can buy in pet shops. You can also use distilled water or rainwater. Distilled water and rainwater are both mineral free and will keep your container cleaner.

What Should I Do When Changing the Water?

When changing the water, you should also rinse your Marimo Moss Balls, as the water and the balls can get dirty over time. After rinsing them, you can gently squeeze them to make sure you clean them well.

It is also a good idea to gently roll the Moss Balls between your hands. Why? Since they no longer live in the freshwater lakes, where the waves brush them and shape them, Marimo Balls can lose a bit of their round shape over time. Gently rolling will also help keep it evenly round and not flattened on one side.

Freshly washed Marimo Balls

Can Marimo Survive Outside of Water? How long?

Yes, Marimo can survive outside of water for a few days, if they are kept moist. When shipped, for example, Marimo is transported in ziplock bags. In those conditions, they can last for a few days, even a few weeks. However, if you let them fully dry out, they can’t survive.

My Marimo Balls, transported in a ziplock bag

Humidity Needs

Marimo Moss Balls live in water, so they require 100% humidity. Once you place them in a container filled with water, their humidity requirements will be met.

Temperature Requirements

In their natural habitat, moss balls live on the floor of cool lakes, where temperatures are lower. According to Balls Of Moss, Moss Balls can live in our homes in temperatures between 63°F(17°C) and 73°F (23°C). But Marimo Balls don’t tolerate well temperatures above 77°F (25°C).

If you have Marimo Moss Balls in the same fish tank with other fish, check the fish temperature requirements. If you keep your Marimo Balls on their own, you can add some ice cubes to temporarily cool down the water during a hot period.

Another factor you need to consider is that glass heats up quite quickly, which is yet another reason to keep your Marimo Balls away from direct sunlight.


Marimo Balls don’t need fertilizer. Still, some people like to use liquid plant fertilizers. Same as with any other fertilizer, if you decide to use fertilizer, stick to the dosage instructions on the package. More is not always better and too much fertilizer can kill your moss balls.

Toxicity To Humans

According to the website, Moss Balls are non-toxic to humans. Still, even non-toxic plants, if ingested, can cause problem such as vomiting as confirmed by the California Poison Control System (CPCS). Try to keep the plant far from children.

Toxicity To Pets

Moss Balls are non-toxic to pets according to the Mossball website. However, California Poison Control System (CPCS) states that moss balls can cause vomiting if pets ingest them.


You don’t need to trim a Moss Ball. These furry algae balls require very little maintenance. Care for Marimo Moss is effortless and quite straightforward. Therefore, you should only trim them if certain parts turn brown. In that case, you can cut off the brown parts.


Moss Balls can be propagated by division:

  • Take out your Moss ball
  • Squeeze it to remove excess water
  • Divide it into two halves with your hands
  • Gently roll the new halves to make them rounder

That’s the whole process. In nature, Marimo Balls would grow a new little Marimo ball that would eventually get separated from the mother plant. When grown in home conditions, you can just split them. Overall, their propagation is very simple.

Common Problems


If your Moss Ball Pet is changing color to brown, this is usually an indicator that something isn’t right. Although Marimo Balls are quite tough and resilient algae, you should pay attention if they change color. There are several potential reasons for the Marimo moss ball to turn brown:

  • when the level of water drops, exposing them to air, the exposed part tends to die off and there is a tendency of developing brown spots
  • It got dirty. No need to worry about it. Rinse it a few times in a water-filled container or under a tap and your furry pet is good to go.


Your Marimo Balls are floating because of photosynthesis. Photosynthesis produces gas bubbles that can attach to Marimo Moss Balls, changing their buoyancy. This characteristic allows them to float in the presence of light and sink in its absence. When the bubbles are created, if they remain attached to the moss balls, you will see them floating.⠀

Check the video below to see Marimo Balls floating:

If you want marimo moss to float, just squeeze the water out of them and put them back in the glass dish. If you try to move them around, you will see oxygen bubbles separating from the Marimo, and some of the Marimo Balls will sink to the bottom. If you don’t touch them, they will usually float for days and then sink to the bottom.

Zebra Mussels

As of March 1, 2021 scientists discovered that invasive Zebra Mussels had been found in Marimo Moss Balls in many different US states. Furthermore, the authorities demanded that Marimo Moss Balls should be destroyed.

Zebra Mussels are incredibly invasive species wreaking havoc in the local ecosystem. When they are in the water, they may change its chemistry. Furthermore, they disturb the food chain and clog water delivery systems.

So how is that related to Marimos? There is a fear that if your Marimo is infested with mussels, when you replace the water in which you keep your Marimos, the mussels could enter the waterways.

Zebra Mussels

Unfortunately, since mussels’ larvae are invisible to the human eye, the US Fish and Wildlife Service (FWS) suggested to destroy your Marimo Moss Balls if you bought them recently. Later however, the FWS added an option to quarantine your Marimo for six months to make sure they are not infested. To learn more about zebra mussels in moss balls and get more detailed on how to quarantine moss balls, destroy them or check if they are infested, check out the linked blog post.

FAQs about Marimo Moss Ball

How to Choose a Healthy Marimo Moss Ball?

You can choose a healthy Marimo Moss Ball by making sure it’s green and it isn’t slimy or slippery. It also shouldn’t have any discolored patches.

How To Tell The Difference Between A Genuine And A Fake Marimo

Telling the difference between genuine and fake Marimo Balls is not always easy, especially if you’re buying one online. Many stores sell fake Moss Balls. If you buy your Marimo Moss balls in person, ask the seller to let you hold the Marimo Ball. If you can change it’s shape, if it is flexible, it is most likely a genuine Marimo Moss. Another thing to pay attention to is the texture of the Moss Ball. The texture will be hairy, not smooth.

If you’re buying a Marimo online, make sure to buy from reputable sellers, such as Sacred Elements (use code MRHOUSEPLANT for 20% off).

Do Moss Balls Grow? And How?

Yes, Moss Balls grow. However, they are slow growers and, on average, grow only 0.2 inches per year (5 millimeters). They usually reach between 2-5 inches in home conditions. They grow faster when you expose them to more indirect light because it will boost photosynthesis, providing food for your Moss Ball.

What do Marimo Moss Balls Eat?

Marimo Moss Balls “eat” light and CO2, which they use to photosynthesize. Still, you can use liquid plant fertilizers if you like. They can boost Marimo Balls’ growth. As with any other fertilizer, ensure you follow the exact dosage instructions on the package. Too much fertilizer can kill marimo.

How to Clean Marimo Moss Balls?

You can clean Marimo Moss Balls by rinsing them under a faucet once every two weeks. You should take out your Moss Balls and dip them in a water-filled container a few times. Or wash them under running water. Gently squeeze them a few times, to rinse them out. You can use tap water. And don’t worry if you accidentally break apart your Marimo Balls. If that happens, you can create a new algae ball by gently rolling it into a roundish shape.

Where to Buy a Marimo Moss Ball?

If you are looking to buy Marimo Moss Malls, look for reputable sellers. And don’t be timid to ask questions. Ask your supplier if their shipments have been inspected and cleared by USDA. Ask what they are doing to make sure their moss balls are not infested with zebra mussels.

Another thing you have to bear in mind is that many shops sell fake Marimo Balls. The best way to check if your Marimo Moss Ball is genuine is to give it a little squeeze. It must be flexible, conforming to your fingers. Unfortunately, many people buy their Marimo Balls online, where it is impossible to test..

One reputable seller of Marimo Moss I can recommend is Sacred Elements (use code MRHOUSEPLANT for 20% off).

What do Moss Balls do in Fish Tanks?

Moss Balls are a decoration in fish tanks but they also help clean the water. Marimo Balls don’t need fish to thrive, they can take care of themselves. However, their beautiful green color, mossy appearance, and low maintenance make them a great addition to a fish tank.

Can I Have Fish or Shrimp with My Moss Ball Pets?

Yes, you can have fish or shrimp with your Moss Ball pets. But, you need to consider which type of fish or shrimp you would pair up with Marimo. Some fish like munching on them. So, if you want to play on the safer side, you should get fish like Betta. Betta fish isn’t an algae lover, so your plants will be safe.

Fish with Marimo Ball Pets

How Long Do Marimo Moss Balls Live?

With proper care, Marimo Moss Balls can live for decades!

How Can I Help my Marimo Moss Balls Grow Faster?

You can help your Marimo Moss Balls grow faster by adding CO2 into the water, by using liquid fertilizers and by providing more indirect light. Marimo Balls, just as other plants, absorb CO2. You can either put your Moss Balls in a container with Seltzer water for a couple of hours or buy a CO2 solution and add it into the container with your Marimo. This will help it grow faster.

When it comes to liquid fertilizers, they can also help the algae growth. However, always follow the dosage instructions since each fertilizer has its own parameters.

Can Marimo Moss Balls Survive in a Sealed/Covered Container?

Yes, you can keep Marimo Moss Balls in a fully sealed/covered container.

Marimo Moss Balls are usually kept in an open glass jar, but you can keep them in a closed one as well

Marimos and Saltwater Tanks

Marimos and saltwater tanks are a combination that can actually work out. Marimo Moss Balls survive nicely in low to mid brackish water. The salinity shouldn’t exceed 1.015 though. Just keep the salinity level in check and react if you see any changes in your Marimo.

Keeping Marimo Round Shape

In order to keep Marimo in a round shape, you need to turn your green algae balls regularly. In their natural habitat, waves gently move Moss Balls around, preventing the sides from being flattened.

Round dark green Marimo Moss Balls

At home, it’s suggested to turn them to keep the roundish shape. Otherwise, the bottom side of your Moss Ball might get flattened.

Why Are There White Deposits on My Marimo Moss Ball Dish?

The white marks on your Marimo Moss ball dish are mineral deposits. Over time water will evaporate, leaving white marks on the dish. The mineral deposits are not harmful to your plant. If you want to remove them, take the Moss Balls out and rinse the dish with the mixture of water and white vinegar.

White deposits on the Marimo Moss Ball dish

More Questions on Marimo Moss Ball Care?

If you have more questions on care for Marimo Moss Ball or any other houseplant, let’s talk.

Always happy to help!

Yours Truly,

Yours Truly,



  1. Pixi January 5, 2023 at 11:01 pm - Reply

    My marimo moss ball is flat on one side and we have started rolling him so he goes back to being round but it wont work. Any tips?

    • MrHouseplant January 6, 2023 at 3:49 am - Reply

      Hi Pixi, you don’t have to be very gentle with it. Try squeezing harder when shaping it. When I’m rinsing mine, I squeeze really hard, they aren’t harmed by it. Even if I can’t change the shape, I don’t mind whether they’re round or oval, they’re still gorgeous :)

  2. Laurie July 24, 2023 at 6:01 pm - Reply

    My miss balls are hard on the outside, as if there is a crust. When I ran them under water, one cracked apart. It is soft and greenish on the inside. What should I do?

    • MrHouseplant July 30, 2023 at 2:54 am - Reply

      Hi Laurie, I wonder if it was exposed to air or to direct sun, which lead to hardening. Is the hard part brown or is it green?

      You could just split the moss ball in two and continue growing 2 separate moss balls.

  3. Jane September 13, 2023 at 5:06 am - Reply

    Hi there, I love mossballs and I currently have 6 of them in a tank, The temp of the water is usually always between 60-70F, I use a filter and a water pump to make sure they move around a lot, 2-3 days a week I’ll put them in the fridge for extra coolness. My problem is 3 of the 6 are a dark emerald green instead of a bright green like how they usually would look. Do you have any advice? :)

    • MrHouseplant September 17, 2023 at 9:53 pm - Reply

      Hi Jane, some moss balls have a naturally darker color. Have your dark moss balls always been dark? If yes, there is nothing wrong with them. If not, try increasing the amount of light. Sometimes moss balls that don’t receive a lot of light will get darker. 🙂

  4. Angela October 26, 2023 at 11:42 pm - Reply

    I’ve been having trouble with my moss balls becoming coated with a slimy substance. I rinse it off, but it always comes back. Do you know what it could be, and how to prevent it?

    • MrHouseplant November 10, 2023 at 1:55 am - Reply

      Hi Angela, the biofilm (slimy film) that forms on top and inside the water is normal. I heard you can use Marimo Salt to reduce the creation of biofilm, but I haven’t tried it personally. If you do end up trying it, please let me know how it worked.

  5. Rhian December 2, 2023 at 8:28 pm - Reply

    I’m new to moss balls, I bought one a few months ago. Was healthy, every water change I have done I’ve put it back into the water and it’s had bubbles and eventually sank. This time however, no little bubbles and it’s just floating on top of the water. Have I been doing something wrong? I noticed as I gave it a little squeeze there was a ‘slit like’ in the centre. Can’t help but think I’ve done something to it.

    • MrHouseplant December 6, 2023 at 10:09 pm - Reply

      Hi Rhian, I don’t think you did anything wrong. I’ve had the same thing happen to me. Sometimes the moss balls would sink, sometimes they would float for a long time.

      As long as it’s green and healthy looking, I wouldn’t worry about it.

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