Marimo Moss Ball (Aegagropila linnaei) Care Guide For Aquariums

Marimo moss balls (Aegagropila linnaei) aren’t actually moss balls at all. 

They’re a unique kind of algae that can grow in the shape of a sphere when it is pushed along the substrate by water currents. It is native to Japan, Northern Europe and Iceland.

In nature, marimo can also be found growing on the underside of rocks or sunken logs, or as loose tufts that can pile up on the bottom of a lake.

Marimo balls are a very popular addition to aquariums where they can add a bit of visual variety. And in this guide, I’ll teach you how to successfully care for marimo moss balls in your own tank.

Caring for Marimo Moss Ball In Aquarium

Marimo moss balls close up on white background

Caring for these nifty balls of algae is really quite simple since they are so undemanding. No need for a fancy setup or lots of effort.

Tank Requirements

Planted tank with marimo moss balls in

Marimo balls require very little water. Some people place them in containers as small as quart jars to use as home decor.

Since marimo balls grow so slowly, there’s no issue with keeping them even in tiny aquariums.

Water Parameters

  • Temperature: 60°-80°F (16°-27°C) 
  • pH: 6.0-8.0
  • dGH: 3-15

Lighting Conditions

This species requires very low lighting (PAR <50).

They actually need indirect light. Marimo balls will turn brown if they’re placed in light that is too intense.

Because of this, they do best in shady areas of the tank, such as corners where light doesn’t penetrate well or in the shadows of decor or plants.

Substrate & Fertilizers

A marimo moss ball does not require substrate, it will just sit on top of the sand, gravel or aquasoil in the tank.

Light fertilization can help the moss ball grow, just be sure not to over fertilize, which could encourage pest algae growth that can harm your marimo. 

Maintenance & Trimming

Marimo balls require very little maintenance:

  • Turning – it’s good to turn each moss ball once a week to ensure that all sides get exposed to the light. If a ball is just left to sit in one spot for too long, it will lose its spherical shape and the bottom will turn brown and eventually die.
  • Cleaning – you should clean your moss ball about once a month. Very gently squeeze the ball in a bucket of dechlorinated water to dislodge detritus and swirl it around in the water to knock loose any clinging particles. 

How to Plant Marimo Moss Ball

If you want the marimo to stay in the shape of a ball, you don’t really plant it at all, you just place the ball in the tank and turn it occasionally.

But, if you’d rather the marimo take on a different shape, you can tear the ball apart, and then super glue the pieces to hardscape, like rocks or driftwood. Eventually, the marimo will become a mat that covers the surface.

Aquascaping with Marimo Moss Balls

Since marimo balls grow so slowly, and stay so small for so long, they’re best placed in the foreground.

Otherwise, they will just be blocked from view by hardscape, plants and decor in the tank. 

How to Propagate Marimo Moss Ball

Propagating one of these little guys is very simple. All you need to do is squeeze the water out of the moss ball, and then cut it in half. 

You can then gently roll each half into the shape of a sphere. 

You may need to tie the ball at first to get it to hold its shape. It’s best to use something that will break down naturally over time, like cotton thread.

Turn the moss balls once a week, and over time, they will grow into nice round spheres on their own. 

Just be patient. Marimo grows very slowly, only 0.2 inches (0.5 centimeters) a year. So it might take them a while to become fully spherical. 

Tank Mates for Marimo Moss Ball

Shrimp on marimo moss ball

Most fish can be kept with marimo balls, and ornamental shrimp will help keep the surface of the ball clean.

Pairing marimo balls with Bettas is really great. Some Bettas will roll the balls around their tank, giving the fish some exercise and mental stimulation and helping the moss balls to maintain their nice round shape.

There are some tank mates to avoid because they will eat or damage your marimo ball: 

Is Marimo Moss Ball Right for You?

This species is very simple to take care of. With the right conditions, they are hardy, long-lived and undemanding.

You only have to turn them every week or so and squeeze them out once a month. No trimming, fertilizing or replanting is necessary.

Marimo balls are an excellent addition to nano tanks. The detritus that gets stuck on their surfaces make the perfect feeding ground for ornamental shrimp.

Many Bettas will play with marimo balls placed in their tanks, helping to provide the fish with important mental stimulation.

I hope you find this article helpful.

I wish you and your fish the very best!

Katherine Morgan
Katherine Morgan

Hey, there! I'm Katherine from Northwest Florida. An aquarium specialist, I've kept tanks for over two decades, enjoy experimenting with low-tech planted setups and an avid South American cichlid enthusiast.

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