Are Moss Balls Alive?

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Marimo moss balls are unique-looking aquatic plants. The perfectly spherical shape makes them look like carefully-crafted ornaments. But they’re very much natural and alive.

So, look no further if you’re searching for an exotic aquarium plant to keep the water clean. The moss ball could be the perfect addition to freshen up your tank.

Are you planning to buy your first Marimo moss ball? Keep reading to learn more about this special plant! I’ll go over everything you need to know, including the care requirements, lifespan, pros of keeping a moss ball in your fish tank, and more.

But let’s first discuss these strange spherical greens’ origins and life cycle.

Life Cycle of Marimo Moss Balls

Marimo moss balls are different from other plants. They don’t grow in the same way and with the same environmental conditions.

This makes for an interesting life cycle. But before we get into that, let’s clarify what a Marimo moss ball is.

Marimo moss balls aren’t moss at all. They’re unique growths of algae (species Aegagropila linnaei). These algae balls can only be found in the rivers and lakes of Japan and Northern Europe.

Moreover, the spherical shape they’re known for is not exactly natural but a result of mechanical action.

Aegagropila linnaei are small, filamentous algae. They don’t need to grow into a ball.

However, the thin hairlike strands entangle and roll together due to the water currents, like a thimbleweed in the wind. And this brings us to the life cycle of a moss ball.

Here’s how they form:

  1. The algae start as single-celled organisms. Soon, the initial cell multiplies and creates small, string-like structures.
  2. A small number of filamentous algae strings entangle together to form an irregular clump.
  3. The water currents push and squeeze the algae until they get a more regular, round shape.
  4. The algae continue to grow, roll, and clump together, forming a sizeable ball.
  5. As the moss ball grows, it develops a small bump (similar to a bud).
  6. The budding part of the ball breaks off to form a new fragment of algae.
  7. The new fragment is shaped by the currents and keeps growing into a new moss ball. Wash, rinse, repeat.

The mechanical action helps them get and maintain shape. It also allows the moss balls to propagate and form “colonies” in the wild.

You can use the same fragmentation method (aka pruning) to multiply your Marimo moss balls in the aquarium.

How Long do Moss Balls Live?

Moss balls are plants. Like any other plant (besides annual ones), they don’t have a specific lifespan.

Theoretically, with constant pruning and propagating, you can keep your Marimo moss balls for a lifetime. A single Marimo ball is commonly said to live up to 200 years or more.

So, you don’t have to worry whether you want to watch your Marimo moss ball grow or create multiple balls to maintain a regular size.

This plant can outlive all of us and then some! Needless to say, it’s a good one-time investment.

How to Care for a Moss Ball?

Moss balls need a few things to stay healthy. Some are passive requirements, like water parameters. Others you need to do regularly.

Here’s how to care for your Marimo ball:

Set and maintain suitable water parameters

The ideal parameters for moss balls include below 77 °F temperature, 6.0-8.0 pH, and up to 1.015 SG. The moss ball might wither and become discolored if the water is too warm, acidic, or alkaline. Be careful if you keep your moss ball in a fish tank, though. Freshwater fish are sensitive to increasing levels of salinity.

Provide suitable light exposure

Moss balls are delicate. Too much light and the moss can burn. Too little light, and the plant won’t produce enough chlorophyll. Ideally, you want the Marimo to get low artificial light exposure daily. I recommend artificial light because it’s easier to control, and LED bulbs don’t transfer heat into the aquarium.

Complete regular water changes

Changing the water frequently is an easy way to maintain a stable pH and prevent harmful bacteria and algae in the tank. All of these things are crucial to keeping your Marimo ball healthy. You should maintain the same water change schedule if you have a fish tank. If you keep your Marimo alone, complete a 50% water change every two weeks.

Clean the moss ball once weekly

Moss balls are easy prey for parasitic algae and fungi. Besides, the spherical form makes it all the more necessary to clean off any gunk that can form on the ball’s surface. If you let the moss ball get dirty, the inner layers of algae can suffocate and rot.

Cleaning the ball regularly will keep the plant safe and healthy. You’ll need a separate container and dechlorinated water to do this.

Gently squeeze and roll the moss ball in your hands to detach the debris on the surface. Don’t worry about messing the shape. You can roll the moss back into a ball once you’re done.

Move the moss ball regularly

Don’t let the Marimo lay on only one side all the time. The moss needs light exposure from all angles. If one side of the ball doesn’t get enough light, you’ll get a dead spot of algae. Remember to flip the ball over for even light uptake.

Are Marimo Moss Balls Good for Fish Tanks?

Marimo moss balls make an excellent addition to your fish tank. Not only do they look nice, but most fish love them.

Moss balls also provide multiple benefits, including:

  • Better water filtration
  • Increased oxygen levels
  • Additional beneficial bacteria
  • Algae prevention
  • No dead plant matter
  • Low risk of accidental tank contamination
  • A source of entertainment for small fish and shrimp

Like other plants, Marimo moss balls suck up nitrates and other harmful compounds from the water. In addition, this ornamental ball’s grassy and multi-layered nature makes it an excellent surface for beneficial bacteria. Moss balls can thus provide additional biological filtration.

Like other plants, they also produce oxygen through photosynthesis, making the aquarium a hospitable environment for fish and other critters.

Moreover, Marimo balls soak up other nutrients in the water, thereby preventing potential algae growth.

Marimo balls only shed if the plant is sick or old. So, unlike other aquarium plants, this ornament won’t produce any dead matter to pollute the tank.

And since we’re on the topic of pollution, you should know that moss balls are among the cleanest decorations for your tank. Unlike driftwood and other plants, they’re unlikely to carry snails, parasites, or harmful bacteria.

Finally, moss balls’ unique shape and texture make them a big hit with aquarium inhabitants. Moss balls collect debris rather quickly. This includes trapped food particles, microalgae, and biofilm due to an accumulation of bacteria.

Small fish and shrimp love munching on these. Bettas and Guppies can also use the moss ball as a play toy, rolling and floating it around in the tank.

Are Exo Terra Moss Balls Alive?

We know that regular moss balls are alive because we can watch them grow and propagate. But what about Exo Terra moss balls?

Well, they look just like moss balls. They function in much of the same way by keeping the water clean. But these are just imitation balls and are not alive.

Exo Terra moss balls contain a hollow sphere made of a special resin material. The resin sphere is covered in real, albeit preserved moss. The moss coating is not alive, as the moss has been dried and covered in a resin coating.

Exo Terra moss balls keep the aquarium clean and odor-free thanks to their absorptive capacity. But they don’t provide the same type of filtration as real moss balls. Since they aren’t alive, they also require zero care and maintenance.

They’re an aesthetically-similar equivalent to traditional moss balls, but they don’t need the same water temperature, salinity level, and light exposure.

They make a good alternative if you want a beautiful ornament, but your fish need warm water or a very low SG level.


Moss balls look so beautiful and unique that you’d think they’re hand-crafted ornaments. However, despite their strange shape, they’ve very much natural, living plants.

Found only in the lakes and rivers of Japan and Northern Europe, these moss balls are actually bundles of filamentous algae that get rolled into shape by water currents.

These moss balls are known for their long lifespan (200 years or more) and low care requirements. Besides being hardy and low-maintenance, they also make an excellent addition to most fish tanks.

Like other live plants, moss balls will contribute to water filtration, produce oxygen, and serve as a hiding or playing spot for fish.

Remember not to confuse regular Marimo moss balls for Exo Terra moss balls! These two look the same. But Exo Terra moss balls are artificial imitations.

Artificial moss balls aren’t real plants, so they won’t act the same way in the tank.

However, these fake moss balls can still help deodorize the tank and keep the water clear.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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