Marimo Moss Balls are very captivating; resembling cute little hairy balls in water. If you hold them in your hand, it feels very silky and soft. Even though theoretically, it is not a ball, but a clump of highly organized algae.

Alongside it, these plants are very easy to attend to and will thrive for a long time with just a little care. And with just a simple propagation technique, you can easily get as many Marimo Moss Balls as you like without ever needing to buy any again.

Significance for Japan

Interestingly, these cute little balls have also been depicted on postal stamps in Iceland and Japan. Moreover, these balls are very special for the people of Ainu and they celebrate a 3-day festival every year for their significance and history.

It is also one of the many things that are renowned as part of their national treasure. Japanese people sometimes refer to the algae balls as “love plants”. Couples tend to give it as a gift to each other to profess their love, as this plant signifies deep affection.

So, if you are wondering about purchasing a few for your tank and want to learn about the tips and tricks to keep them healthy in the tank for a long time, do follow the rest of the blog.

All about the Cultivar

Quick Species Facts
Scientific Name Aegagropila linnaei
Other Common Names Cladophora Ball, Moss Ball, Lake Ball
Family Pithophoraceae
Origin Japan and Iceland
Lifespan Unknown
Max. Length 8 to 12 inches (20 to 31 cm)
Type Freshwater

History, Origin and Natural Habitat


The evidence of Marimo Moss Balls was first documented during the 1820s by an Austrian botanist. Additionally, the name ‘Marimo’ was given by a botanist in Japan- Tatsuhiko Kawakami, during the late 1890s.

The name Marimo has a slightly different meaning- ‘Mari’ stands for a ball and ‘Mo’ stands for algae. So, even though it is made of tiny algae, it was termed moss because it resembled more moss-like features than algae.


The origin of Marimo Moss Balls come all the way from Japan – Lake Akan. But it has also been found to have another origin in a European region- Lake Mývatn, which is a lake in north of Iceland. Some are also found in the Shatskyi lakes of Ukraine. These, however, are mostly used for showcasing in aquarium shops rather than selling (ref).


They are primarily found in freshwater lakes with cool temperatures, as implied by the preceding paragraph. Also, that is why they are also referred to as “Lake balls” (ref). They are most commonly found in distinct patches at the bottom of lakes at depths ranging from 2-2.5 m (6.6-8.2 ft).

Their natural habitat has a low to almost moderate density of aquatic flora and fauna. In addition to that, the calcium levels found in their habitat range from moderate to high concentrations (ref).

Growth Forms of Marimo Moss Balls

Marimo Moss Ball has three types of growth forms, based on their interaction with the environment-

On rocks

They can grow on rock faces, mostly on the underside or shaded region of the rock. They do not have a ball shape, but rather a patch like normal algal growth.

Free-flowing filaments

These algae can also live as free-flowing, having a single filamentous-like structure in lakes. These stick to the water beds and, as a whole, give the bed of the lake a carpet-like appearance.

The signature ball shape

The most desired shape of the Marimo moss is its ball-like appearance. It is a solid structure of algae, with a round shape made up of filamentous structures.

Size: How Big Do Marimo Moss Balls get?

Their growth rate is approximately 5mm per year in the wild and in captivity, without any growth-enhancing factors.

Most Moss Balls have a size of 1.75 to 2.25 inches. But they can achieve a maximum size ranging between 8 to 12 inches (20 to 31 cm) if they remain undisturbed for a long time (ref).

Author Note: In captivity, the growth can be slightly enhanced if we keep them in optimal water conditions, with a timely day and night cycle.

What Do They Look Like?

Just like the name denotes, they are round, just like a “ball”. Their round appearance is due to the continuous wave-like motion of the lake water, which makes them tumble and roll around the water bed. This tumbling and rolling causes it to grow in a ball-like shape uniformly (ref).

Moreover, they are algae, so they have a green pigment (chlorophyll) just like plants, giving them a green color.

But they are not only green on the outside but also on the inside as well. If the outside portion receives any damage, the inactive chloroplasts (chlorophyll-containing cells) start photosynthesis.

Fake Marimo Moss Balls

It is not uncommon for shop owners to make fake Marimo Moss Balls and sell them at original rates. They make use of regular moss (which is not algae) as it looks similar to the Marimo algae, to recreate a fake ball.

They wrap the regular moss around a ball made of plastic or Styrofoam to give it strong structural support.

Sometimes, they don’t even bother with that, they just take a bunch of moss and mold them roughly into a ball. However, they fall apart faster than the ones that have a core.

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It is quite tricky to spot a fake one from a real one. So here are some things you can do to identify the real ones from the fakes-

  1. Cut it in half to check the inside. It should be green all the way through, without the presence of any kind of core or kernel.
  2. The growth of the Marimo algae is radial, i.e., the growth starts from the center and then extends out from the middle point as it grows in size.
  3. The inside of the Marimo will look more organized and sturdier than the fake moss one.

What’s Their Life Expectancy?

Due to their slow growth rate, it can take a few years for them to reach their full size. In addition to that, the longest recorded life span of these algae was estimated at over 200 years.

But even then, it is impossible to guess how long these Marimo Moss Balls can live for. So, if you decide to get a few, prepare yourself for years to come.

Where to buy Marimo Moss Balls?

These are not found frequently in local shops. However, they can be bought from online stores. The reason behind this is that these algae balls are quite rare.

A single piece from an online store can vary from $5 to $7. If you buy them in bulk, they can go for $50 to $100.

Their price, however, depends mostly upon the degree of roundness and general state of the balls. The rounder and healthier it is, the higher the price.

Marimo Moss Ball Care Guide

Planting in an Aquarium

It is very easy when it comes to putting them inside the aquarium. Unlike the plants, they don’t really have roots so you are free of this extra work of planting them in the substrate.

There is simply just putting them in the water and leaving them there, that’s it. But there are a few things that you should check before you put them in the tank-

  1. If you have them from a store, they can get a bit dried up and hardened. So, you can soak them in filtered water or even your tank water for about 20 to 30 mins which will help them to regain their structural integrity.
  1. While soaking them, change the water a few times to remove the dirt or debris that may have come with it. More importantly, this also helps to get rid of unwanted things that could have hitch-hiked themselves to the Moss Balls while buying.

Author tip: Make sure that the water temperature does not exceed 78 °F during the resoaking procedure.


If you decide to keep them in their ball formation, they won’t require any fertilizer to grow. This is because they are not planted in the substrate where the fertilizer will be used.

Moreover, in order to make food, they take nutrients and minerals directly from the tank water. So, you can add supplements like Nitrogen, Potassium, and Phosphorus tablets to the water, but use only a few.

Maintenance & Trimming

As you know, Marimo Moss Balls are nothing more than simple, hairy balls of moss. So, there isn’t much you need to do to maintain their shape.

They grow outwards in a uniformly radial fashion, naturally. But if they are kept undisturbed in a place, the underside may not grow properly.

So, in order to maintain a uniform round shape, keep turning it every few days so that all of the faces can grow at an equal rate. This will ensure a round shape for a long time.

Additionally, if you still feel it is growing unevenly, you can use a pair of scissors to trim the excess parts to make it more round. Do not feel worried, as it is totally safe to trim a few uneven parts.

How to Propagate Marimo Moss Balls?

If you are thinking of getting more Marimo Moss Balls for your aquarium, then let me tell you that you don’t need to go to a shop anymore.

You can get more from your existing ones just by using a simple method known as vegetative propagation.

It is the method of severing a specific part of a plant and letting it grow into an adult without the need to acquire seeds from it.

As Marimo moss is a type of algae, it doesn’t produce seeds but can be easily multiplied using the technique of propagation.

So, just follow these easy steps and you will have numerous balls in no time-

Step 1

First, take out the balls you wish to propagate. Make sure it is big enough to be cut into pieces of two or three. But before that, squeeze the water out of it and rest it outside for a while to drain out any excess water from it. Be gentle while squeezing as they are very delicate.

Step 2

Now, using a sharp razor or knife, cut the ball into two to three equal pieces. If the cut pieces appear to be bigger than 2-3 inches, cut them again into equal halves. Now. You have 6-8 pieces of Marimo balls you can propagate.

Step 3

Now you can’t just leave the cut pieces by themselves and put them in the water. You first need to reinforce their shape, or else they will grow unevenly.

For that, take a string and bolster it around the moss in a cross-like shape to roughly give it a spherical shape and tie a knot on it, just like you would do when you tie a ribbon onto a present.

Step 4

Now, put the cut pieces into the tank, or you can also use glass jars or transparent high-grade plastic jars filled with fresh aquarium water. Make sure it receives enough light to carry out its photosynthesis. Also, make sure the water temperature does not exceed 78 degrees Fahrenheit.

Step 5

Now, after placing it in the tank or jar, you have to turn it regularly every few days. This will ensure that light is received on all sides, or else it won’t grow up to be round. Turning it periodically will ensure proper growth and shape of the ball overall.

Common issues to contemplate for Marimo Moss Balls

Floating Moss Ball

A problematic thing that you may face while keeping Marimo Moss Balls is that they tend to float some days and sink after a while. This is a very unusual phenomenon that may throw some people off if they don’t know the reason behind it.

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But it is not something you should worry about. It is very normal for them to do that. The reason behind it is purely based upon the bi-products (gas) formed when they make food during the day.

As you know, plants release oxygen from their leaves as they carry out photosynthesis. So, during the day, Marimo algae also produce food using light, which in turn results in the formation of bubbles of oxygen.

These bubbles get trapped inside their fuzzy structure and make them buoyant enough to make them float. However, these bubbles stop forming during the night, and so they drop down back into the bottom of the tank, slowly (ref).

And sometimes, it can even take days for them to sink down again as the bubbles stay trapped inside. You can give it a gentle squeeze to release and remove all the bubbles.


By the way, floating is not the only problem they face. Sometimes, when one side gets too much light or inadequate light, they tend to turn brown.

This can happen if they are kept stagnant at a single location without any movement from external factors. It can sometimes be hard for aquascapers to keep a continuous flow like lakes.

When this happens, the side that does not get enough light starts dying and turning brown. In addition to that, if they also receive too much light, it can lead to bleaching effects and they will slowly start turning brown. In any case, that is why it is advised not to keep them in direct sunlight.

Falling apart of Moss Balls

If you ever witness your Moss Balls falling apart, do not get scared. It can happen sometimes, but it’s nothing to worry about.

In this situation, the best thing to do is pick up the fallen pieces and mold them back together into a ball with your hands.

If you are facing problems holding them up together, you can just use a string and tie it up for a week’s duration. It will take some time for it to reform back into shape.

7 Benefits of Marimo Moss Balls

In addition to just being a good decoration, there are also many other benefits to keeping Marimo Moss Balls. Some of them are mentioned as follows-

Oxygenation of tank water

As mentioned before, they are algae, so basically, they are just tiny plants. So, they produce oxygen while carrying out their basic metabolism, i.e., photosynthesis.

 It takes in carbon dioxide and releases oxygen as a bi-product of its food production. This helps keep the aquarium water rich in oxygen without the need to install any extra apparatus.

Food for small crustaceans

Due to the fuzzy, hairy-like appearance of the ball, particles of food tend to get trapped inside it.

 These are then consumed by small crustaceans such as shrimps, crabs, and even snails and small fishes. These can help the shrimp to thrive in a competitive environment.

Beneficial microorganisms

Marimo Moss Balls can prove to be a good home for many bacteria, which could be beneficial for the tank.

These bacteria help in the decomposition of leftover food and fecal matter of fish and help to keep the tank clean. This, in a way, also helps in controlling the growth of bad microorganisms in the tank.

No dead leaf issues

These cute little algae balls are very easy to maintain. Regular plants have leaves, which shed to the bottom of the tank and start to decompose quickly.

These do pollute the tank if not removed with haste. Marimo balls do not have leaves like other plants, so you won’t have the headache of scooping up the dead leaf matter from the substrate.

Reduction of nitrate levels

Another benefit of keeping them is that they reduce the nitrate levels in the water. They take in the nitrate biologically available in the water and use it to grow.

However, the level of nitrogen consumption is not very significant, but it’s still better than nothing. It can help slightly to keep the nitrogen levels in check.

Control of excess algal growth

Because of their nature, they are in direct competition with plants, which also include free-growing algae in the tank. As they take up nutrients for themselves from the water, the unwanted algae begin to starve and die off, keeping the tank relatively clean.

Different decorative purposes

There are many aquarists who become quite creative with these algae balls. As you know, these are quite soft, so their shape can be altered with just a little force.

So, people who like to aquascape have found ways to alter their shape into different decorative items. Some have opened them and flattened them like a grass carpet, spread onto the base of the tank.

Some aquascapers like to put them over rocks and boulders and fully spread them over the surface to give the appearance of algae-covered rock found in wetlands.

Many have even put them in the branches of an artificial skeletal structure of a tree, making them look like a bonsai tree inside the tank.

Some don’t even put them in aquariums, but rather they put these Marimo Moss Balls into jars of different sizes and showcase them on tables and other places.

Terrarium Recommendations

Quick Tank Facts
Water Temperature 43 °C to 75 °F (6 °C to 24 °C)
Minimum Size Any size, as long as it can fit the ball
Water Hardness 2 to 20 dGH
pH Level 7.0 to 8.0
Lighting Subdued to moderate
Calcium levels Moderate to high
Type of water Freshwater to slightly brackish

Terrarium Size Requirements

There isn’t any particular requirement for keeping the Marimo Moss Ball. As long as the water parameters are good, they can even be kept in small jars in big aquariums.

However, it is easier to maintain the parameters of smaller tanks than the bigger ones. But if you are proficient in all these things, you can easily keep them in any kind of tank.

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Terrarium requirements for your Marimo Moss Balls


Use subdued lighting while keeping them in the tank. They live in a low-lighted environment in the wild but are able to tolerate up to moderate lighting in captivity. You can use LEDs and fluorescent lamps to fulfill your lighting needs.

But make sure to provide them with the proper day and night cycles. This will ensure that their biological clock is not disrupted, even in artificial conditions.

Pro tip: Make sure to avoid halogens or incandescent lamps that could potentially increase the temperature of the water.


All kinds of substrates can be used, and it is mostly a matter of the preference of the aquarist. However, it’s suggested that you avoid the substrates that could harm or scrape the Moss Balls, like gravel, stone chips, etc.

It is rare as these are soft and mushy, but still, there is a chance. So, a safer option would be to use fine sandy material emulating the sands found in lakes. Round pebbles can also be a good option for the tank.


All types of decorative items can be used. Some people get really creative by combining these balls with other decorations to make them even more attractive.

Tank apparatus

Tank apparatus like filters or air pumps will not serve much of a purpose for Marimo Moss Balls. The reason behind this is that they already produce oxygen in the form of bubbles that come out of them.

So, the water will always be properly oxygenated for the fish or other organisms living in the tank. Moreover, the algae balls use the free-floating nutrients in the water for their sustenance. So, only use filters if there are a lot of fish so that the water doesn’t get too murky.

A quick tip: You can put a carbon-di-oxide pump in the tank as they require adequate levels of CO2 in the water to make food for themselves.

Water Parameters

To keep your Marimo Moss Balls healthy, you must maintain certain parameters so that they do not feel stressed as they are living like other plants.

  • Maintain a temperature range of 43 °C to 75 °F (6 °C to 24 °C). The cooler the water, the better it is for them.
  • The hardness of the water should be between 2 to 20 dGH. They prefer a soft freshwater environment.
  • The pH should be kept neutral but should not go above 8.0. You can use chemical buffers to keep the pH at 7.0.
  • It has been observed that their natural habitat has moderate to high levels of calcium. So, you can take calcium supplements to keep the calcium levels in your tank suitable.

Suitable Tank Mates

Marimo Moss Balls can live peacefully with most fishes. Its resilient nature, along with its water parameter requirements, also enables it to coexist happily with many other invertebrates, not just fishes.

A few good examples of compatible tank mates are as follows-

  1. Most non-aggressive fish species (e.g., Bettas, Guppies, Danios, etc.)
  2. Snails (e.g., Nerite snails, Ramshorn snails, Mystery snails, etc.)
  3. Shrimps (both Caridina and Neocaridina genus)
  4. Smaller brackish water fishes (Archerfish, Gobies, Columbian Shark Catfish, etc.)

It can sometimes be difficult when keeping Caridino genus shrimps as they require a bit more acidic pH compared to the neutral to slightly basic pH needs of the Moss Balls.

Pro Tip: Try to avoid Cichlids, Goldfishes, Plecos, etc., and other big fish species that may feed on or damage the Moss Balls. Also, crayfish and crabs are not considered good companions for them.

Story behind Marimo Moss Balls

According to myths and legends, the story behind the Marimo Moss Ball is quite fascinating. There was a tribe known as the Ainu Tribe situated nearby Lake Akan in the Hokkaido islands of Japan. The daughter of the head loved an ordinary person. They wanted to get married, but were not allowed to do so.

As a result, the disheartened couple ran away from the tribe, but misfortune struck them and they fell into Lake Akan and drowned. Legend has it that the bodies of this couple slowly transformed into Marimo Moss Balls, and that is the reason this plant symbolizes love and good luck to the people of Japan.

Frequently Asked Questions

Are Marimo Moss Balls safe for turtles?

Yes, they are absolutely safe for turtles, even if they are ingested by them. They are like every other plant that lives with turtles.

But if the Moss Balls die for any reason, you should remove them as soon as possible. The reason behind this is that they will start to decompose soon enough and it will become toxic for the turtle if it eats them.

How many Marimo Moss Balls can be kept per gallon?

Several Marimo Moss Balls may be put together in a gallon of water, which is roughly 4 liters. They are small and do not require much living area. They may flourish even when multiples are clumped together.

Are Marimo Moss Balls poisonous to cats?

No, they are harmless to cats or any other pets. They are just algae that may look a little weird but are absolutely safe for animals. Cats are generally not interested in the Moss Balls, let alone eating them. So, it is safe nonetheless.

Are Marimo Moss Balls legal/safe to purchase?

Yes, they are not illegal and you can safely purchase them all around the world, with the only exception being Japan and the US.

In Japan, these algae balls are considered sacred to them and have symbolism for their culture. So, that is why they are not allowed to be bought or sold in their country.

In case of the US, Moss Balls imported from any country have been banned from retailing because it encourages the growth of Zebra mussels. These Zebra mussels are an intrusive species that clogs water pipes and damages the ecosystem. It costs the government a fortune to resolve these issues (ref).

Final Thoughts: Are Marimo Moss Balls considered a good pet?

These unique-looking algae balls are one of a kind. They require minimal care if the tank conditions are properly maintained. And you don’t have to worry about them getting old and dying, as they will outlive most of your fish and plants.

Moreover, the benefits it provides to the tank make it a valuable addition to your aquarium. And if you are worried about getting more of them, a simple technique will enable you to get multiples from a single one. If all of these qualities do not make it a good pet worth buying, then I can’t say what will. Just maintain cool water temperatures alongside a dimly lit setting. This will ensure your Marimo Moss Ball is comfortable and healthy.

About the Author

Shelby Crosby

Shelby is a passionate fishkeeper who has been writing about fish for over 5 years. She is a pro aquarist and holds a BSc Honors Degree in Wildlife and Fisheries. She creates her own beautiful aquarium layouts and loves to share her knowledge of tropical fish with other hobbyists.

Career Highlights:

  • Has worked with several aquarium manufacturers as a consultant
  • Organized and hosted workshops on freshwater fish keeping at retail stores, educational facilities, and libraries
  • Released content for the amphibian community through her writings

Educational Highlights:

  • BSc Honors in Wildlife and Fisheries in 2011 (University of Northern British Columbia)
  • Completed her undergraduate thesis on the effects of zoochlorella supplementation on the growth and health of fish.

Writing Experience

Miss Crosby is a Freelance blogger; many of her articles are posted online on various blogs. She has also written a few short articles for "Tropical Fish Hobbyist Magazine" in the past. She is a regular contributor to Her education, first-hand experience with fishkeeping, and in-depth knowledge in aquaculture make her one of the most competent writers in the industry.

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