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Marimo Moss Balls Care Guide
marimo moss balls care guide

Marimo Moss Balls Care Guide

If you’re in search of a hardy aquarium plant with a unique and vibrant appearance, Marimo moss balls may be just what you’re looking for. The Marimo plant is a beautiful species and can be a great addition to your aquarium for its visual appeal and water filtering properties. 

Marimo moss balls (Aegagropila linnaei) can only be found in certain parts of the world. They are harvested from lakes in Scotland, Estoria, Japan, Iceland and Ireland. They naturally form into a spherical shape due to the currents of the water in which they live. 

These freshwater moss balls can survive for centuries with proper care—so be ready for a long commitment. Their longevity makes them quite popular in Japan, where they’re considered good luck charms and are often passed down from generation to generation. Use this Marimo care guide for tips on how to make sure your new plant pet is happy and thriving. For even moresolutions to help keep all your aquatic life flourishing, check out our fish deals.


Don’t let the name fool you—the moss ball is actually a type of algae. They are almost perfectly spherical and vibrant green in color when thriving. Their fun appearance makes them stand out, and they can be a great centerpiece in any aquarium. 

This fascinating plant takes a long time to grow—which makes perfect sense, considering the average Marimo moss ball lifespan. They typically grow about 5 millimeters a year. If you keep your Marino in an aquarium, they usually grow to be between 2 to 5 inches. Marimo plants can grow even larger in their natural habitats—moss balls from Lake Akan of Japan have been known to reach 12 inches in size.

Plant care

Marimo balls typically require very little maintenance, but routine water changes should be provided to replenish minerals and prevent a buildup of waste.. Make sure to keep the water in your habitat on the colder side. If your Marimo temperature is higher than 82 degrees Fahrenheit, they may protest by developing brown spots. 

Because they create their own food, there’s no need to worry about feeding your moss ball or giving it fertilizer. It’s also perfectly fineto house your Marimo with other live plants. If you keep it cool and dimly lit, aquarium moss ball care is usually minimal. 

Aquarium requirements

Good news—your little round moss ball is adaptable to many different types of aquariums. In fact, they don’t need to live in an aquarium at all—Marimos can thrive in just about any kind of container.  

While these moss balls can tolerate different types of aquarium lighting, too much light can cause your bright green friend to develop brown spots. Keep your habitat away from direct sunlight. Indirect sunlight or basic home lighting is usually sufficient. Gently rotate your Marimo periodically to ensure even exposure on all sides. 

Marimos are freshwater plants, but they usually do well in habitats with a slightly higher level of salinity. Adding a bit of freshwater aquarium salt to the water may perk up your plant and help keep them vibrant. Just make sure the added salt won’t hurt any other inhabitants of your aquarium. 

How to plant your Marimo moss ball

Planting your new aquarium resident is relatively easy—you simply drop the moss balls in water. You may notice your Marimo moss ball floating around in its new habitat, which is completely normal. Floating occurs because oxygen bubbles are trapped inside your new plant. You can hold your Marimo under the water and softly squeeze the bubbles out or just let them dissipate naturally. 

Maintenance and care 

Believe it or not, your pet algae can actually cause more algae to grow. One of the perks of homing a Marimo in your aquarium with fish is that they may take care of thisproblem for you, as some species of fish willeat the offending excess algae off the moss ball. 

Marimos are generally velvety in feel. If your moss balls don’t have any algae-eating roommates, they may get slimy and require a bath. 

Bathing your Marimo is simple—

you can put them in a small container of clean, dechlorinated water and gently roll and squeeze them in your hand a couple of times  until the gunk is gone. 

While bathing, you may want to take the opportunity to make sure your moss ball is retaining its shape. Since they are formed by water currents in nature, Marimos can lose their signature sphere-like structure over time. You can gently roll the moss in your cupped hands to get it back. 

Like any aquarium-dweller, your algae plant will benefit from a clean habitat. If your Marimo lives alone, it’s recommended that you remove and replace half of the water every couple of weeks.  If your Marimo moss ball is housed in an aquarium containing  other aquatic life, it may stay clean for longer.


Marimos often propagate themselves. They go through the asexual reproductive process called budding, where a bump grows and eventually breaks off to form a new algae ball. 

However, you can also propagate them yourself. Make sure you use a good-sized plant—young, smaller Marimo moss balls may not be a good choice for manual propagation. 

Gently remove your Marimo from their home and squeeze out the excess water. To propagate, simply cut it in half with a knife or a sharp pair of scissors. Gently roll each half between your palms to form a sphere and wrap with string to retain the shape. 

Aquarium mates and compatibility

You can house your aquatic moss ball with most freshwater fish. They pair particularly well with bettas—bettas typically love to play with the Marimos and bat them around the aquarium. There are, however, a few species to avoid:

  • Goldfish
  • Plecostomus
  • Dwarf crayfish

These algae-loving aquatic life may treat your Marimo as a delightful snack and chow down on your plant. Keep your moss ball separate from these aquatic species, and keep an eye on other bottom feeders to ensure they don’t eat your moss ball for dinner.

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FAQS about Marimo moss balls

Marimos are great for aquatic hobbyists who want unique and unusual plant life in their aquariums. Many Marimo enthusiasts also see their little plant balls as pets and give them names, as their fun shape and velvety texture almost make them look like small animals.

Marimos are also popular gifts for children in Japan due to the ease of taking care of them and their reputation as good luck charms. They’re cute, fuzzy and can make great aquatic decorations.

Yes. Marimo balls can help keep your aquarium clean. They often absorb waste and nitrates produced by aquatic life, which helps filter the water and discourages the growth of more harmful algae. They also brighten your aquascape and give your aquatic life a sort of living toy. Just make sure the needs of your moss ball fit with the other residents of your aquarium.

If you want to keep an aquarium, bowl, vase or mason jar exclusively for your Marimo, you can style it with decorative gravel, aquarium décor and other compatible live plants.

If you want to keep an aquarium, bowl, vase or mason jar exclusively for your Marimo, you can style it with decorative gravel, aquarium décor and other compatible live plants.

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