Marimo Moss Ball Care 101: Your Questions Answered!

marimo moss algae ball care

At Thoughtful Garden, we receive many questions about plant care, but no plant eludes more new gardeners than the Marimo moss ball. These cute little balls of algae are typically found floating through freshwater lakes in Japan, Scotland, Iceland, and Estonia, but make for serene decorative indoor plants if you know how to take care of them.

We’re here to save you from hours of Googling with the answers to the most common question about Marimo moss ball care. Let’s get started!

Wait, so they’re not actually moss??

That’s right! Don’t let the name fool you, Marimo moss balls are actually a rare form of spherical algae. In fact, the word “Marimo” actually means “seaweed ball” in Japanese because of the habitat the balls thrive. It takes a while for these things to grow, typically around 5mm per year. There isn’t a center stone or hidden crystal inside the Marimo moss balls; they’re just solid algae!

As you probably know, algae are a living creature technically, so it needs proper care just like any other pet would. The cool thing about Marimo moss balls is that they can live for over 100 years if you take care of them. Talk about a pet you can pass onto the next generation!

How do you keep them from turning brown?

This might be the most common question that we get. Many new growers find that their beautiful moss balls turn brown relatively quickly and they can’t figure out where they went wrong. Where you place your Marimo moss balls can greatly impact their lives, especially the light that they are exposed to.

These little guys are used to floating in cool lakes in Japan and Scotland, and when placed in direct sunlight, their water will get way too warm for them to survive. We recommend putting them in an area of your home that doesn’t receive intense light so they can stay nice and cool. If they do turn brown, move them to a cooler location, and they should be able to recover on their own. If not, try adding a pinch of aquarium salt to the enclosure.

How to Keep Them Round

Marimos naturally develop their round shape by rolling across the lake floor. Since there isn’t a current in your home, they might start to fall apart or develop flat spots over time and lose the signature round shape they are known for. Don’t panic! This is entirely normal. To help them get back to that spherical shape, gently roll them around in your palms as you clean them. If you are gentle, it won’t harm them and will help them get back in shape!

Let’s Talk About Water

As with any aquatic plant, the water that they’ll be living in is crucial to their survival. These are the temperature and water parameters you should keep in mind:

Water Temperature: 63– 73° Fahrenheit
Water Types: Most freshwater aquariums are suitable, and tap water is fine.

Many have found success with saltwater tanks as well; however, you need to keep a close eye on the salinity of your water. Brackish water with salinity levels up to 1.015 are perfectly fine and may actually be beneficial in keeping your moss balls green and healthy.

When it comes to changing the water, we recommend that you do a 50% change every two weeks. For best results, you should let the water sit out for 24 hours before adding it to the tank. Keep in mind that depending on the fish that you’ll have in the enclosure and the climate of your home, you might need to change the water more frequently. Do some experimenting and find the interval that works best for you!

To clean your enclosure, treat it like any other aquarium. Simply use a brush to clean the sides of the tank walls to get rid of any excess algae that might collect there over time. Also, while changing the water, you should clean off your moss balls. Gently squeeze them to flush out any dirt particles that might be trapped inside and roll them around gently to get them back into shape.

Can they survive outside of water?

The short answer is yes, they can. However, since their natural habitat is in water, it is recommended you don’t keep them out of the water any longer than a week or so. That being said, some have had success storing Marimo balls in open air terrariums for up to a month.

Are they safe for fish?

This answer depends on the type of fish that you have. In most cases, moss balls are 100% safe for fish, and it’s actually the moss balls you should be concerned about. Certain species like Goldfish, Pleco fish, and other aggressive fish that travel in schools will usually eat the moss balls.

On the other hand, solitary fish like Beta fish are great tank-mates because they don’t feed on algae. Plus, the contrasting colors of the fish and the moss balls will make for a nice decorative piece in your home.

Why do they float?

Marimo moss balls float because of an air bubble trapped inside of them. This is completely normal and nothing to be concerned about. If you want your moss balls to sink to the bottom, you can simply give them a light squeeze to release the air trapped inside but be careful not to squeeze them too hard and change their shape! Typically, moss balls will float when you first toss them into the tank but will sink to the bottom after only a few days.

Marimo moss balls are great additions to your home! Whether you’re putting them inside your fish tank or in a Marimo terrarium, these living creatures add a wonderful splash of color and vitality to any home, and you can keep them around for years and years to come! Check out our Marimo product now and stay tuned for even more in the future from Thoughtful Garden!

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