Marimo Moss Balls are one of our very favorite plant discoveries of the last few years. Marimo are equal parts bizarre and beautiful, and Marimo moss ball care is very easy.

Marimo Moss Ball Cartoon

Marimo, a Japanese word which literally translates to “seaweed ball” are not moss at all - they’re actually a rare form of spherical algae. There’s no central stone or kernel inside the sphere - it’s solid algae, radiating from the center, growing radially outward at the snail’s pace of just 5mm per year. But in their natural habitats - few fresh water lakes in Japan, Estonia, Iceland, Scotland and Australia - they’ve been known to grow to between 8 and 12 inches in diameter!

Another reason to love Marimo moss balls is beautiful lore that surround these mysterious aquatics. Legend tells of two lovers who desired nothing more than to be together. When their love was forbidden, they fell into the water, and their hearts became Marimo balls. Marimo are said to bring your heart’s desire to both giver and receiver.

And of course, we love Marimo because they live forever. Well, not forever, but easily 100+ years. For this reason, we often joke that Marimo make wonderful family heirlooms.

Marimo moss ball care is quite simple. Here are a few guidelines.

Marimo Moss Ball Aquariums


Keep your Marimo where they will receive llow to medium indirect light. You must protect marimo from the direct rays of the sun, as Marimo can easily turn brown if they are getting direct light! Also keep in mind that direct sun will be intensified by glass marimo enclosures which can heat water quite quickly. Remember - these guys are native to cool lakes, and should be kept cool.

Marimo are well adapted to low light spaces and can photosynthesize in normal household light. If your space has no window, keep marimo close to a fluorescent or full-spectrum bulb.

Changing the Water

Change water once every two weeks using regular tap water (for best results, allow water to sit out for 24 hours prior to changing the water). You’ll need to change the water more often in summer, as it will heat and evaporate more quickly. Clean your marimo enclosure with a brush if algae begins to grow on tank surface.


If your marimo turn brown, make sure they’re moved to a cooler location with less direct light. They may recover and turn green again on their own. If not, you may add a tiny amount of aquarium ocean salt.

Why are my Marimo Balls Floating?

More than likely, your Marimo balls have an air bubble trapped inside that is causing them to float! Gently squeeze your marimo balls to pop the air bubble. Generally, Marimo will sink to the bottom of their tank within 1-2 days of being added to an enclosure.

Can Marimo Survive Outside of Water?

Yes! Marimo moss balls can survive without water if kept in plastic or a closed jar for several days, as long as they aren’t allowed to fully dry out. Plastic bags are the easiest way to travel with Marimo moss.

Keeping Marimo Shape Round

In their natural habitats, the waves and currents of the lakes gently rotate and roll the Marimo balls along the floor of the lake.

To ensure that Marimo stay keep their round form and don’t flatten out, you’ll want to gently agitate the water in your Marimo enclosure, with the goal that when your Marimo balls settle back to the bottom, they rest on a different side than they had prior. Try to simulate the gentle waves of a lake.

Marimo and Aquarium Safety

Many people ask us if Marimo can go into their fish tanks. We’re happy to report that Marimo are welcome additions to freshwater aquariums. In fact, they naturally absorb toxic nitrates in water and act like miniature filters, cleaning the water.

Though Marimo are safe for your fish, some fish are known to enjoy Marimo a bit too much and may peck at and eventually destroy a Marimo ball. Keep a good eye on things and see how your fish react before you decide to permanently leave Marimo in a fish tank.

Follow these Marimo moss ball care guidelines, and you should see your little guys thriving in no time! Have any questions or your own best practices for marimo moss ball care? Share with us in the comments!

Pistils Nursery


I truly appreciate all the tips and tricks! I’ve had my Marimo balls for over 4 years now! I actually love that they float and a tip I was given when I bought them was to add a few splashes of Perrier or another plain bubbly water and that keeps them floating or allows them to rise to the surface… It’s fun and cute! I also use distilled water. I’m going to see if they can go in with my little fresh water goldfish (without the bubbly water of course ;)

— Babyb

Hi, I just bought 2 Mossballs for my small freshwater fish tank three weeks ago. What should I feed them? I cleand my tank last night and gently ran fresh water over them to clean them from some old fishfood. Then put them back into the clean tank. Thank you so much for any kind of help and advice! 😊

— Shawnie Alford

Hi I was wondering if they need any food and I know they may be just little balls but just in case will they need anything of the sorts?

— Emily

My Marino arrived in excellent condition. I would like to know if using Puffy Ball Food, 1drop per ball in water 1x, per week,is good or not necessary? This is an aquarium.

— Bonnie Hackett

Hi thanks for your informative site, I have a Marimo Moss Ball which was put into quarantine tank with an Anubias plant, I just purchased weeks ago… I didn’t notice with the naked eye but the plant had white cotton wool like fungus on (prior to the ball going in) which was clearly visible in blown up photo images. Will this affect the ball which has been in that tank for 5 days already, and if so how would I treat the Marimo Moss Balls to get rid of the fungus if necessary…it still looks ok….

— Ru

Can you place many marimo on top of each other?

— Wilson Fujinaga

Can anyone tell me if a betta fish likes warm water and the Marimo moss balls like cool….how is it that I can put a Marimo moss ball in the tank and expect it to survive?

— Karen Schneider

Hi and thanks for the post. If i cut the ball and place one half over a rock in quiet water, will it take roots in the rock and grow over?

— Sergi

They are so cute

— bob

hi! i am very new to the plant care life and i just discovered these cute balls. thank you for the very straight to the point and beginner friendly tutorial on these cuties !

— grete

If you have a glass jar with a lid you dont have to change the water as often. I have had my marimos for about 1.5 years and have only changed the water three times. As long as there is not too much sunlight or heat they are extremely hardy and make a beautiful centerpiece. I recommend for anyone who has little light sources and difficulty tending to terrestrial plants :)

— Kat

Does anyone have any good websites they bought they’re from that are actually real (that ship to uk)? Thankyou

— Sophie Lane

I recently got a Marimo ball and I absolutely love it! I named him Mochi:)

— emily

Great web site you’ve got here.. It’s difficult to find quality writing like
yours these days. I honestly appreciate people like you!
Take care!!

— Nelly

does the container the moss balls live in need to be covered or can it be open to the air?

— g