Marimo Moss Ball (Aegagropila linnaei): Ultimate Care Guide

Marimo Moss Ball (Aegagropila linnaei) is one of the most popular moss plants in the aquarium hobby industry. This moss ball makes a great addition to any tank because of its simple care requirements, interesting shape, and adaptability to various habitats. These rare forms of algae are utilized to improve water quality within a tank by creating oxygen and removing nitrates from the space. Marimo Moss Balls are only found growing in a few lakes in the world, located in Japan, Iceland, Scotland, Ireland, and England. These moss balls are considered a naturally endangered species in many parts of the world, but they are commercially grown in abundance.

In Japan, Marimo Moss Balls are considered good luck charms, because they are known to live 200 years or longer. They are even kept as family heirlooms that get passed down through generations to promote prosperity and grow larger the longer they are around. Marimo Moss balls are thought to symbolize close bonds among family members and friends of close connection. These moss balls are also identified as a symbol of everlasting love and make popular gifts among those in romantic relationships.

While Marimo Moss Balls appear nearly perfectly round in shape, they are created entirely by nature with no human interference. As the algae strings grow in the lakes these plants are found in, the slight movement of the waves in shallow waters causes the soft and fuzzy algae to gradually work itself into a sphere. These moss balls appear with a texture that is best described as both fluffy and velvety in nature. Marimo Moss Balls also take on a sponge-like consistency when submersed in their aquatic ecosystem.

Can You Keep Marimo Moss Balls as Pets?

Because of their simple care requirements, Marimo Moss Balls are known to act as pets for young children. It is not uncommon for individuals to keep this plant as a pet and watch it grow through generations.

Do Marimo Moss Balls Need Food?

Marimo Moss Balls do not need to be fed any plant food or pellets because they create their own source of nutrients through photosynthesis. Like other plants, these moss balls are able to absorb light and convert it to a food source that sustains their life.

Marimo Moss Ball (Aegagropila linnaei)
Marimo Moss Ball (Aegagropila linnaei)

Benefits of Keeping Marimo Moss Balls in Your Fish Tank

There are many benefits to keeping Marimo Moss Balls in a fish tank, with the most well-known being their ability to absorb harmful nitrates and toxins from the water. In large quantities, nitrates can stress and kill the fish in an aquarium. Marimo Moss Balls act like filters and suck up the nitrates around them.

Marimo Moss Balls also maintain the water quality in the tank by removing waste and other unwanted substances from the space. They create small amount of oxygen that are of benefit to any tankmates they may have. Marimo Moss Balls also harbor a decent number of good bacteria, which can increase the overall health of the tank.

Marimo Moss Balls benefit an aquarium habitat by making excellent decor with their vibrant green color and unique shape. These moss balls add an element of foliage to any tank they reside in and are known for their ability to attract gazers. Marimo Moss Balls also help to engage tankmates by acting as toys, mimicking the functionality of balls, where other fish that are easily bored can push them around and stay entertained by their rolling ability.

Marimo Moss Ball Care

Marimo Moss Balls are very low maintenance aquarium members and can even live in tap water. Depending on the conditions, water in the tank should be cleaned at least every two weeks to ensure that the Marimo Moss Ball does not suffer from a build up of dirt or waste. The Marimo Moss Ball will need cleaned from time to time by getting removed from their tank and squeezed a few times in clean water before returning to the aquarium. They should also be rolled around a few times in an owner’s hands to ensure they keep their spherical shape.

How to Keep Marimo Moss Balls in an Aquarium?

Marimo Moss Balls thrive and grow by absorbing nitrates, phosphates, and organic waste from the water in their aquarium. Because they enjoy cleaning up after other organisms, Marimo Moss Balls will most enjoy living in a habitat with tankmates. A few tankmates that might not cohabitate well with the Marimo Moss Ball are Plecos and Goldish because both species like to eat green algae, and might consume the moss ball.

Although they have very few specific care requirements, it is important to ensure that the Marimo Moss Ball is not exposed to too much direct light. They also prefer water that is mildly brackish in salinity, so adding a small amount of sea salt to the Marimo Moss Ball tank can be beneficial if they are experiencing adverse health effects. These plants can be kept in glass tanks, with room temperature water, and an average amount of natural or artificial lighting.

How Many Marimo Moss Balls Should You Keep Per Gallon?

Is it important for Marimo Moss Balls to have enough room to grow and flourish, so one gallon should hold one to three of these unique plants. Marimo Moss Balls interact just fine together since they are plants, so there is really no limit to how many can exist in one tank as long as there is enough room for each to live healthily. These plants are popular in both small and large tanks due to their adaptability in a variety of aquarium spaces.

Lighting Requirement

Since Marimo Moss Balls naturally form at the bottom of lakes, they do not typically require any specific or high intensity lighting to be happy in their tank. Household lightning or indirect sunlight are enough to allow this plant to photosynthesize in its habitat. If the Marimo Moss Ball is exposed to light that is too intense or direct, they might begin to form white or brown spots on their surface. If these colors begin to appear, the moss ball will need to be removed from the light source to avoid illness or even death. Marimo Moss Balls are green all the way around and can photosynthesize with light no matter which direction they are facing in the tank.

The Marimo Moss Ball might need to be manually flipped if it is stationary for a long time to ensure that all of its sides receive adequate light. In its natural habitat, the moss ball is shifted gently by the motion of the lake current but because this does not happen in an aquarium, they will need to be moved by their owners. An alternative to manually rotating the Marimo Moss Ball is to give it a tankmate that is curious enough to use it as a toy and move it around in the process of play.

Marimo Moss Ball (Aegagropila linnaei)
Marimo Moss Ball (Aegagropila linnaei)


Because the lakes Marimo Moss Balls are found in are typically cold, these plants do the best in cooler water conditions. Marimo Moss Balls should be kept in water with a temperature no higher than 76 degrees Fahrenheit, or else brown spots might appear on their surface. If the water temperature becomes too hot, they can be placed in a refrigerator for up to 48 hours to cool down. Although they can be revived in a refrigerator, it is important to note that the Marimo Moss Ball will die if placed in a freezer.

Water pH

Since Marimo Moss Balls can survive in tap water, a pH balance between 6.0 and 8.0 is ideal for their habitat and happiness. These moss balls can also thrive in water that has slight salinity and even rely on sea salt in small doses to heal them when ill. Marimo Moss Balls typically occur in most abundance in habitats that are not strongly impacted by acidification.

Marimo Moss Ball Growth Rate

Marimo Moss Balls grow extremely slowly, at a rate of about 5 millimeters in diameter per year. They take a long amount of time to become significant in size, but some owners still expect them to reach the large sizes they do in their natural habitat. When kept in captivity, it is very unlikely that a Marimo Moss Ball will grow larger than a few inches in diameter.

Marimo Moss Ball Growth Size

On average Marimo Moss Balls grow to between 1.75 and 2.25 inches in diameter. Occasionally, these plants will grow to 3 or 4 inches in diameter, but this only occurs among older Marimo Moss Balls. The largest Marimo Moss Ball ever recorded was around 12 inches in diameter, found in a natural habitat.

Co2 Requirement for Marimo Moss Ball

While injecting carbon dioxide into a Marimo Moss Ball aquarium is not necessary for their survival, it can be beneficial in encouraging growth. The more carbon dioxide that exists in the aquarium, the quicker and larger a Marimo Moss Ball is likely to grow. The increase in carbon dioxide allows the moss ball to photosynthesize at a faster rate, creating more of a food source and speeding up to growth process.

Marimo Moss Ball Propagation

When maturity is reached, a Marimo Moss Ball will put out smaller buds that can get detached from its surface and develop into individual moss balls. One large Marimo Moss Ball can also be broken up and divided into smaller pieces. This process of propagation will create new, nano Marimo Moss Balls that can then grow on their own.

Dead Marimo Moss Ball

Marimo Moss Balls will appear brown and lifeless if they happen to die. These plants can also accumulate algae on their surface that will cause them to suffocate and die off. Marimo Moss Balls can also get sick and a change in their color is a strong indicator that something is wrong with their health. If the moss ball is turning white in color, it is probably receiving too much light and if it is overly slimy in texture, this is the result of hostile algae that can choke the Marimo Moss Ball.

Can a Marimo Moss Ball Die?

A Marimo Moss Ball can die if its living conditions do not meet its optimal requirements. A habitat that is too extreme in water temperature or that has very low light quality can send a Marimo Moss Ball into shock and even end its life.

What Does a Dead Marimo Moss Ball Look Like?

A dead Marimo Moss Ball will appear white, brown, or black in color on its surface, rather than the vibrant green it is known for. There might be algae on the moss ball that is an indictor of poor health.

Can You Revive a Dead Marimo Moss Ball?

A dead Marimo Moss Ball has an opportunity to be revived if it is moved to a cooler, less lit location. The aquarium tank should be cleaned if any algae is present on its surfaces and the Marimo Moss Ball might return to its original green color. If these steps do not help revive the moss ball, a little salt water can be added to their habitat to aid in healing the plant.

Why is My Marimo Moss Ball Floating?

Marimo Moss Balls floats when there are air bubbles trapped inside of them. To remove the air bubbles, gently squeeze the plant while it is under the water to release the trapped gas. While Marimo Moss Balls often sink, when they perform photosynthesis, the extra oxygen can cause the plant to float and this is a normal sign of a healthy moss ball. When photosynthesis stops and light fades, the moss ball will fall back to the bottom of its tanks.

Why is My Marimo Moss Ball Falling Apart?

A Marimo Moss Ball falling apart is a sign of bad health and decay. These moss balls deconstruct from the inside out and will being to fall apart of they are experiencing adverse health conditions. If there is a hostile algae on the surface of the Marimo Moss Ball or if it is simply too big for its space, it might begin to self-destruct and crumble into pieces.

Are Marimo Moss Balls Good for Betta Fish Tanks?

Marimo Moss Balls are great additions to Betta fish tanks. Because Betta fish are easily bored and love to explore, they will often push around and play with a Marimo Moss Ball in their tank. Betta Fish also enjoy resting on things in their natural habitat and may use the moss ball as a spot to lay their head. The Marimo Moss Ball makes a great decoration and toy for any tank with Betta Fish.

Where Can I Find Marimo Moss Ball for Sale?

Marimo Moss Balls can most easily be bought through online retailers, and they come in a variety of sizes. Aquarium stores might also be able to order in Marimo Moss Balls for purchase upon request. Marimo Moss Balls are sold for an average price of 15 to 25 dollars, falling on the lower end of cost on the aquarium hobby spectrum.

Because some stores sell artificial and fake moss balls for aquariums, it is important to pay attention to ensure that the moss ball being purchased is an authentic Marimo Moss Ball. Artificial moss balls are usually plastic and covered in synthetic hair, which can be fairly easy to differentiate from the real thing. If they are being sold in pre-packaged plastic and not from an aquarium tank, this is also a good indicator that the moss ball is not real.

Marimo Moss Ball and Zebra Mussels

Zebra Mussels are one of the most destructive invasive species in North America and there is a large concern that they are contained within Marimo Moss Balls.

Do Marimo Moss Ball Contain Zebra Mussels?

Zebra Mussels have been found in Marimo Moss Balls that are sold at pet supply stores, garden centers, florists, and online retailers. These mussels can grow in population very quickly and cause damages to their ecosystems.

Considering the potential risks of adding Marimo moss balls to aquariums, some aquarists have decided to incorporate other types of aquarium moss as an alternative, such as Java moss.

Potential Dangers of Zebra Mussels in Marimo Moss Balls

Zebra Mussels are known to impact their environments by disrupting the food chain, smothering native mussels, changing water chemistry, clogging water intake structures, and littering beaches with sharp shells. If Zebra Mussels are found in Marimo Moss Balls, they should be reported and disposed of by the “destroy, dispose, and drain” method developed by the U.S. Fish and Wildlife Service. This method includes first destroying the moss ball by either freezing, boiling, or bleaching it. After destroying, the moss ball will need to be disposed of by placing it in a plastic bag and throwing it away in the trash. Finally, the aquarium will need to be drained and decontaminated with either hot water, salt water, or bleach.