Marimo Moss Ball Care Guide – Planting, Growing, and Propagation

Marimo moss ball (Aegagropila Linnaei)

Marimo moss ball is a type of green algae (Aegagropila Linnaei) which is famous for its use in the hobby. Marimo moss ball comes from ‘Pithophoraceae’, a family of green algae. Therefore, this species cannot be classified as a moss, aquarists refer to it as a ‘moss ball’ because of its resemblance to a typical moss.

Marimo is a species of filamentous green algae commonly found in lakes in the northern hemisphere. It bears other names like Lake ball, Cladophora ball, Mossimo, Lake ball pets. Moss ball is used in the aquarium for decorating the foreground and midground, it is a slow-growing species and most suitable for planting in shrimp tanks where it serves as a foraging or grazing ground for shrimp.

Keep reading for more information on the Moss ball; interesting facts and how you can care and maintain it successfully in an aquarium.

Marimo Moss Balls – check out the price on Amazon

Quick Notes about Marimo Moss Balls

Common Name Marimo Moss Balls
Other Names Lake ball, Cladophora ball, Mossimo, Lake ball pets
Scientific Name Aegagropila linnaei (Cladophora aegagropila, Cladophora sauteri)
Tank Size (minimum) 5-gallon (~20 liters)
Difficulty Easy
Lighting Low to medium
Optimal pH 7.0 – 8.0
Water hardness    Very soft – very hard
Temperature 43 to 75 F (6 – 24C)
Substrate Not needed
Growth Rate Slow to moderate
Placement in Tank Foreground / Midground 
Height up 20-30 cm or 8 – 12 inches
Not needed – Low
CO2 Not needed – Low
Propagation Splitting and re-rolling them

Different Forms of Aegagropila Linnaei

As a matter of fact but Aegagropila Linnaei can occur in several different growth forms, depending on environmental conditions:

1.   Free-floating unattached mats, where little tufts start growing and floating throughout the water.
2.   Carpet type (attached growth form) on the shaded sides of submerged rock.
3.   Fragmented type or ball type, which is, by the way, is the rarest type!

Different theories about the shape-giving formation of the ball form have been proposed. However, it is generally assumed that the formation is a mixture of mechanic processes through water motion and features intrinsic to the species that help entanglement, such as the stiff texture, the formation of rhizoids, and the growth pattern while rolling on the sediment. Rolling movements on the sandy bottoms induce radial growth and profuse lateral branching.

Although all of the forms have the same characteristics, fluffy, velvety and a bright, but deep green color. A recent study from Japan also contributing to the conservation of Aegagropila linnaei and the management of its habitats indicates the possibility of genetic differentiation between different growth forms, and it emphasizes the necessity to extend conservation efforts as well.

Marimo moss ball (Aegagropila Linnaei) as carpet

Partly because of the popularity of the intriguing ball form, Aegagropila linnaei is one of the few freshwater algal species that has been listed as threatened on several red lists of endangered species. This form of algae is included in the national red lists of Belarus, Estonia, Germany, Japan, Russia, and Sweden.

Origin of Marimo Moss Ball

Marimo moss ball was discovered in Sweden in 1753 by Carl Linnaeus who collected some ball samples. The Moss ball was first described in the 1820s by Anton E. Sauter, which was found in Lake Zell, Austria. Friedrich T. Kutzing established the genus ‘Aegagropila’ with Aegagropila linnaei as the species based on its formation of spherical aggregations. Aegagropila linnaei was once placed in the genus Cladophora and was renamed as Cladophora aegagrophila. After a series of thorough and extensive DNA research, the name was returned to Aegagropila linnaei.  The return to its initial naming was due to the presence of chitin in the cell walls (traits that are normally present in plants) which distinguishes it from the genus Cladophora.

Going forward, the moss ball was named Marimo by Japanese botanist – Takuya Kawakami in 1898 when he found them along Lake Akan in Hokkaido, Japan. The name Marimo means ‘Ball seaweed’, ‘Mari’ implies bouncy ball and ‘Mo’ means plants that dwell in water.

In recent times, Marimo has been declared as a national treasure, the Ainu people of Japan hold a festival every October on yearly basis as part of their sacred culture. The indigenes of the community prohibit the collection of Marimo moss balls from the lake.

Marimo moss ball (Aegagropila Linnaei) in aquariumAccording to taxonomy, Marimo moss ball can be classified as following:

Kingdom: Plantae
Phylum: Chlorophyta
Class: Ulvophyceae
Order: Cladophorales
Family: Pithophoraceae
Genus: Aegagrophila
Species: Aegagrophila linnaei

Habitat & Ecology of Marimo Moss Ball

Marimo moss ball can be found dwelling in cool freshwater and brackish habitats, few lakes in the northern hemisphere with higher latitudes – which are generally regarded as its typical habitat, examples: Lake Akan in Japan, Lake Myvatn in Iceland, Lake Naardermeer in North Holland and Lake Zell in Austria.

Huge Marimo moss ball (Aegagropila Linnaei)They can also be found in rivers, for instance, epilithic form has been found in the Seine and the Moine in France, in River Sasso in Switzerland, the Féynes spring in Hungary, in the Oslava River in Czech Republic. Another notable habitat is the brackish northern part of the Baltic Sea, where it grows mostly attached to rocks.

The round form of the Marimo is maintained by gentle wave actions that occasionally turns in its natural habitats. Lake Akan in Japan is home to large Marimo balls where they reach a perfectly round and formidable size (up 20-30 cm or 8 – 12 inches) and shape (like a bowling ball). Marimo balls often exist in dense colonies.

Description of Marimo Moss Ball

Marimo is a very slow-growing algae species. Its growth rate has been recorded to be 5mm (0.2 inches) per year and it takes a long time to gain a significant amount in size, you shouldn’t worry about this species overtaking your tank.

In the wild, the lake balls can reach 8 to 12 inches in diameter, but commercially available versions are sold at 2 inches or smaller.

The structure of the Marimo balls is unique, there is no core or kernel in the center of the balls. The algae filaments grow in all directions from the center of the ball, continuously branching out and thereby laying the foundation for the spherical form.

The balls are sizeable, spherical and green in color, which ensures that they can photosynthesize like other green plants. Inside the balls are also green and packed with dormant chloroplasts that contain chlorophyll which become active in a matter of hours if the ball breaks apart. It possesses cell walls that contain cellulose and they store carbohydrates in the form of starch.

In a tank set-up, the Marimo is suitable for midground or foreground placement in the tank. 

Tank Requirements and Water Parameters

Tank size:

This species can fit in any type of vessel and tank regardless of the size. From plastic /glass containers, jars, vases to 5-gallon (20-liter) tanks and much more. The Marimo moss ball is undemanding and it will be a good option for nano tanks.

Water type, Temperature, Hardness, and pH:

Temperature: Since the natural habitats of the Marimo Moss Balls are lakes with cool temperatures, they can cope with temperature conditions ranging from 6-24° C (43 – 75F). When the water temperature gets high, consider moving the balls to a cooler area. Overheating can lead to the destruction of the Moss balls, they will simply fall apart.

pH: Marimo moss ball appreciates water with pH in the range of 7.0 to 8.0 for optimal growth and maintaining good health conditions.

Hardness: The plant can thrive in a wide range of water hardness conditions, it can withstand general hardness in the range of 2 to 20 dGH. It can also grow in brackish water as well.

Calcium: According to the results of research, the preferred habitat of Marimo Moss Balls is inferred to be oligomesotrophic lakes with moderate to high calcium levels. In the course of this study, only five habitats of Marimo Moss Balls were found with a pH below 7, and only eight lakes were reported to have low calcium levels. This indicates that Aegagropila linnaei typically occurs in habitats that are not strongly affected by acidification.


Marimo Moss Balls does not require any special or high-intensity lighting since they naturally occur at the bottom of lakes where there is little to moderate light exposure. To that effect, indirect lighting or artificial lighting in low intensity should be enough for the Marimo moss balls to photosynthesize and grow.

Intense lighting from direct sunlight exposure and high-intensity LED lighting will harm the balls and result in the formation of brown spots on them. Place them in areas with lower light levels in the tank.

Read more about it in my article “Advanced Guide to Planted Tank Lighting”.


Any type of substrate is fine for the Marimo. However, in aquarium, gravel substrates are most suitable for this species because sand or soil-based substrates will get entangled in the threads of the algae balls, and will make the cleaning process more stressful and tiring.


CO2 and fertilizer application: Marimo will appreciate additional CO2 supply and fertilizer application although it is not compulsory, and they can as well do without them. The application has a little significant impact on its growth since they are an extremely slow-growing species but it will help them stay healthy and strong.

Important: If you keep shrimp in the tank, I would highly recommend reading my articles:
CO2 in a Planted Tank Guide
CO2 in a Shrimp Tank

How Copper Affects Dwarf Shrimp
Shrimp Safe Plant Fertilizers
The point is that a high level of CO2 and Copper (most fertilizers contain copper) is extremely dangerous to the shrimp.

Planting & Propagation of Marimo Moss Ball

Everything about this species is easy and that includes planting. After obtaining some moss balls from the aquarium store, rinse them in aquarium water and introduce them into the tank thereafter. There is nothing simpler than this.

Propagation is equally easy, after a while the mature Marimo Moss Ball will put out buds / daughter plants that get detached from the main plant. You can as well split the moss balls into many smaller pieces and place them into the tank and growth continues.

Maintenance and Care of Marimo Moss Ball

This species is easy to maintain and care for. However, there are a few rules: you have to carry out regular water changes, clean the moss balls, keep it in shape, provide cool water, and do not use algae removing products, they will kill the Marimo ball too.

Let’s go into full details:

Water changes:

Regular water changes help to prevent dirt and waste from building up on the moss balls. Regardless of the vessel you are growing the Marimo Moss balls in: it could be a bowl, jar or in the tank; you still have to carry out water changes from time to time. I will recommend you do this every one to two weeks, if you are keeping the Marimo with other plants and animals, then you should do a 10 – 20% water change.

Note: Once again, if you are in shrimp keeping hobby, DO NOT do big and (or) frequent water changes. It can cause molten problems for your shrimp.

Cleaning the Moss balls:

Due to the fine thread algae filaments of the Marimo Moss balls, it is easy for dirt, debris and organic matter particles to get trapped in the balls. You can clean the balls by removing it from the tank, gently washing and squeezing it a few times (to ensure it is clean) in a container full with clean water and put back into your tank.

Important: Do it at least once a month, ideally every two weeks, and use only dechlorinated water!
Tip: Clean it with water from a water change.

Cool water:

The Marimo Moss balls prefer cool water conditions since it occurs naturally in cool lakes. In the tank, provide water temperature conditions of less than 24 °C (75 F) and keep the tank away from direct sunlight.

During summer when the temperature is hot, consider moving the moss balls to a cooler place for a while. The Moss balls can be placed in the refrigerator during the hot period, however, DO NOT allow it to freeze.

Change positions:

If the moss balls seem to be out of shape or falling apart, roll it in your hands for a little while. Since the Marimo is no longer living in a lake where the motion of waves which helps to keep it in shape, this can be substituted by rolling the ball gently with your palms to regain its spherical shape.

So, move your Moss ball around systematically to maintain its ball shape and prevent rotting.

Benefits of the Marimo Moss Balls

  • Aesthetics: The unique form and shape of the Marimo moss balls make it a great decorative addition to any kind of tank set-up. The balls can as well be made to take different decorative forms in the aquarium. They are a popular choice in an aquascape.
  • Oxygenation: Just like other aquatic plants, Marimo uses up CO2 and provides oxygen in the tank as a result of the photosynthesis process, and this is needed by aquatic animals for survival.
  • Grazing ground for shrimp: Marimo moss balls serves as grazing or foraging ground for inverts and small fish. Tiny bits of food get trapped in the algae filaments which the shrimp can graze on. This is a good way to improve your shrimplets survival rate.
  • Helps cycling: The unique structure of moss balls harbors a good amount of beneficial bacteria.
  • Maintenance: Marimo Moss balls do not produce any waste in the tank, unlike other plants that do shed their leaves which fall to the bottom of the tank and rot thereby polluting the tank water. The moss balls do not produce wastes unless when they die, which is very uncommon.

As a tiny bonus:

  • Reducing nitrates: Although Marimo Moss balls can help you to reduce the nitrate level, consider it as a small bonus. It funny to see how some articles include Moss balls in top/best aquarium plants to reduce nitrates. Seriously? Of course, they use ammonia and nitrates to grow, but … they grow very slowly! As a result, their consumption rate is also pretty low. Unless you fill the tank with lots of Moss balls – do not expect any result.

Note: To reduce the nitrate level significantly, you need to have fast-growing plants, which take nutrients from the water column. You can learn more about it in my article “Nitrates in Shrimp Tank. How to Lower them”.

  • Helps against excess algae growth: Actually, this is the same situation as with nitrates. Marimo sucks up the same nutrients which algae need for its growth, thereby competing with nuisance algae. I’d like to point out that competing and out-competing is not the same thing. Even more, this is mostly possible in smaller tank set-ups with lots of Moss balls. Once again, do not really count on it if you need results right here – right now.

Problems associated with Marimo Moss Balls

Marimo Moss balls are extremely hardy but that doesn’t mean that they cannot become unhealthy. Here are some of the problems that plague the Marimo and how you can treat them effectively:

Brown Marimo: This is a sign of uncleanliness and it is often due to the build-up or accumulation of dirt on the balls. What you need to do is to bring out the Marimo balls from the tank and squeeze it out in a bowl of clean water. Add a bit of salt to the water to stimulate the Marimo’s growth. If you notice that one side of the ball has a brown tint, it is a sign indicating that the Marimo is not getting enough light. In this case, turn the Marimo around a bit more often to ensure that all parts get enough light.

White Marimo: Marimo turns white when it is getting too much lighting. When this happens, place it in a slightly shady part of the tank.

Slimy Marimo: If you notice that the moss balls feel a little bit slimy, it is due to the presence of other algae attached to it. You can eliminate this by washing them off, or else they will choke and harm the moss balls.

Marimo Falling Apart: You may notice the moss balls falling part, don’t panic! All you have to do is to pick up all the pieces and roll them together until they form a big ball again. Alternatively, you can collect the pieces and reshape them into smaller balls. After this process, ensure that they are getting enough light.

Black Marimo: Your moss balls can develop blackened parts over time, this is a rare condition whereby the Marimo starts to decay from the inside due to the presence of hostile algae on them or if clean water doesn’t reach the inside. When you notice this, remove the Marimo from the tank water and get rid of the blackened parts, roll them to get back into shape. This procedure will give them a chance of survival and the growth process continues.

Marimo Moss Ball and Tankmates

The hardy and sturdy nature of the Marimo moss balls makes it compatible with most aquatic animal species.

Marimo moss ball (Aegagropila Linnaei) and shrimpLake balls can coexist peacefully with the following aquatic species:

Do not worry about Amano shrimp, Nerite snails or Otocinclus catfish. Although Marimo moss ball comes from a family of green algae, this algae eating team will not hurt it.

Aggressive fish species like Plecos, African Cichlids, Angelfish, Goldfish should be avoided.

Most types of crayfish and crabs will be bad neighbors as well.

Buying Marimo Moss Balls

Marimo Moss ball is a rare species and not easily found in local aquarium stores. You can source for this species online on Amazon or any other reputable online store.

You should bear in mind that a fake Marimo exists. Here are some of the pointers to note when buying this plant:

  • The fake moss balls are made with a soft plastic ball wrapped in synthetic green hair.
  • Most fake balls are not kept in the planted tanks, rather they are sold pre-packaged or kept in the decorations section.
  • Fake Marimo looks perfectly smooth, a real Marimo should have some slight bumps on it.
  • Real Marimo moss balls can be picked apart and equally reshaped by rolling it between your hands.
  • Real Marimo balls will float for some time if you squeeze out all the water from it. There should not be any air bubbles on the inside of the ball.

Interesting facts about of Marimo Moss Ball

Marimo is an amazing species and these are some interesting facts about it:

  • Marimo moss balls are extremely slow-growers, they grow about 5mm each year and it takes many years to reach their maximum size.
  • The lake ball growth form is almost extinct in most lakes, however, the attached form still exists.
  • Marimo can grow without air supply hence they can thrive in air-tight containers.
  • They are almost indestructible. When they fall apart, they can be easily reshaped and growth continues.
  • In Japan, the Ainu people hold a three-day festival every October yearly at Lake Akan as a part of their culture.
  • The Marimo has been a protected species in Japan since the 1920s, and in Iceland since 2006. Lake Akan is protected as a national park and Lake Myvatn is protected as a nature reserve.
  • Collection of this species in its natural habitats (in countries like Japan and Iceland) is strictly forbidden and prohibited.
  • The lake balls are sometimes used as souvenirs, lucky charms to toys and cartoons.

In Conclusion

Aegagropila linnaei balls have also become extremely popular in the aquarium trade in recent years.

Marimo is excellent for beginners in the hobby because of its hardy nature and easy care. This algae species can tolerate a wide range of water temperature and hardness conditions, it is extremely durable and almost indestructible! Another interesting quality is that they can thrive for a long time, 50 – 100 years in the wild and up to 10 years in a tank set-up if they are properly cared for.

Marimo Moss Balls – check out the price on Amazon

13 thoughts on “Marimo Moss Ball Care Guide – Planting, Growing, and Propagation

  1. I could not refrain from commenting. Exceptionally well written!

    1. Hi Brandee Arton,
      Thank you 🙂
      Best regards,

  2. I do consider all the concepts you have introduced on your post. They are really convincing and can definitely work. Nonetheless, the posts are too quick for newbies. May just you please lengthen them a bit from subsequent time? Thanks for the post.

    1. Hi April Matinez,

      If you have any questions, do not hesitate and ask me.
      I will gladly try to help.

      Best regards,

  3. Thank you, I have just been searching for info about this subject for a while and yours is the best I’ve discovered till now. However, what concerning the bottom line? Are you sure in regards to the supply?

    1. Hi Kisha Spaw,
      Thank you!
      Do you mean my link to check the price on Amazon in regards to the supply?
      Could you elaborate a little bit?
      Best regards,

  4. I was able to find good information from your content.

  5. Hi Michael, thank you so much, this guide is very well written. I have some questions: Can I use tap water or it is better to use bottled water? I must keep a gravel substrate or it can survive without it? Does it provide nutrients?

    1. Hi Eugenia,
      Thank you!
      Can you use tap or bottled water for what? For cleaning Marimo moss ball or keeping?
      As for cleaning, you can use any water.
      If you are asking about keeping, in this case, I would not recommend using bottled water.
      The point is that bottled water or distilled water does not have minerals and trace elements. So, it will not be optimal for the Marimo moss balls.
      It really does not need any substrate in the tank. Moss balls get all their nutrition from the water, that is why too clean water is not good for them.
      Best regards,

  6. Hi Michael,
    I think my moss ball is about to have babies or something! I had it in my turtle’s tank, but my turtle started ripping apart my moss balls. I took it out and put it in a glass of water on my window sill. I went on vacation, and when I came back it had a bunch of lighter green lumps on it and a lighter green film around it.

    1. Hi Wendy,
      I don’t think that putting your Marimo moss ball on the window sill was a good decision.
      First of all, too much light can harm it. Second, I suspect that it is just covered with other types of alga, because of the high lighting.
      I hope to be wrong on this matter but it would be better for you to check it very closely.
      Best regards,

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