Magnificent Marimo

January 26, 2012

Until recently, I had never even heard of marimo, but I saw a picture on Pinterest and immediately fell in love. They are so cute! Since I am insistent on killing a plant in every genus known to man, I ordered myself some. They arrived a few days ago and are seriously adorable, though considerably smaller than I expected. I’m still learning about the little balls of cuteness myself, but I thought I’d share some photos and interesting info that I’ve learned about their care and feeding, so to speak, so far.

From L-R we have named them Jeb, Franklin, and Marge.


Marimo is a Japanese word that literally means “ball seaweed” (mari is a bouncy ball and mo is a generic name for water plants) though you might also see them called lake balls or moss balls online. Despite the confusion the names might cause, marimo are technically neither a seaweed nor a moss; they’re actually a somewhat strange form of algae that grows in a sphere as it’s rolled along a lake bottom.

Aegagropila linnaei, as they are known in the scientific world, are fairly rare and are only found in freshwater lakes in Iceland, Scotland, Japan, and Estonia. Why so rare? A sphere is actually a very impractical shape for a plant to take, giving it a low surface-area-to-volume ratio. Additionally, marimo require very specific conditions to thrive, needing cool waters, low light, and constant movement caused by waves or currents to turn them. In many parts of the world where they occur naturally their populations are declining, even with the help of conservation efforts that have made them a protected species.

Sadly, I can’t expect my marimo to get all plump anytime soon. Even in ideal conditions, the balls grow very slowly with most packing on less than 5 mm per year. At least I won’t have to reinvest in containers for them all the time.

Giant marimo in Lake Akan (from Wikipedia)


According to the instructions that came with my little guys, they’re pretty easy to care for, so hopefully I won’t kill them.

Water: Marimo can survive quite happily in tap water that has a moderate pH. Don’t use distilled water as the marimo need the minerals in natural water to survive. Some sites advise against using tap water as there is chlorine added, so perhaps rain water would be best? I really am not sure, but mine seem fine in tap water for the moment. Water must be changed every one to two weeks to keep it fresh, more often in the summer and less often in the winter.

Temp: Marimo don’t really like to be hot so you should ideally keep them in moderate temps. If you can’t keep them cool during in the summer months, stick in them in the fridge for a bit during the hottest part of the day. Just make sure they don’t get too cold, as they will not survive freezing.

Light: You might think that your marimo would love to get bright light, but that might actually kill it. Marimo are adapted to low light conditions and can get burned by the sun (you’ll see brown spots) so keep it in indirect or artificial light only.

I really hope I can keep these guys going until they get nice and big! It’s said that taking good care of a marimo will make all your wishes come true

Marimos chillin. They are in the light for photo purposes only!

Fun stuff

  • During the 1920’s in Japan, it was cool to gather marimo from Lake Akan and display them in the home, and many, many people harvested marimo from the wild. The added stress of a hydroelectric dam upriver from the lake  caused them to start dying off in great numbers. An appeal was made to the Japanese people to return their marimo to the lake in an attempt to help the marimo recover. An enormous amount of people responded, and in 1950 the first marimo festival was held at Lake Akan to commemorate this outpouring of support.
  • One of the coolest things I’ve noticed about my marimo is that they can rise and sink. When I first got them they were mostly floating, probably from being packed in a dark envelope for several days. Once they started getting light, they sunk back down to the bottom. It’s strange to think of a plant being able to move in this way, but they really do! Some websites say marimo can also roll themselves, repositioning for better light and to shake off sediment.
  • Marimo is known as the “love plant” in Japan because of an old myth that tells of a chief’s daughter who fell in love with a commoner. Since their love could never be in their human forms, they changed into marimo and lived happily ever after at the bottom of a lake.
  • Marimo balls in their natural habitat break apart when they get too large.  The inert algae in the center is able to start photosynthesizing on its own within 4 to 6 hours of coming into contact with light and immediately starts making a new marimo.
  • There is a popular character in Japan called the Marimokkori. Marimo for the algae balls and mokkori for erection. See below for a link to a picture of one of these hilarious guys.

I wish my marimo were this big. Image from Nancy O. on Flickr.


Want to learn more? Check out these great sites and shops!

Marimo Great reference and place to buy marimo.

Marimo Wiki: All the basics about marimo.

Video of marimos hanging out in a tank (they don’t look real!): This is just kind interesting.

Info about wild marimo in Lake Akan: Learn more about how marimo grow in the wild.

Marimo Company with adorable marimo cartoons: This Korean company has all kinds of little marimo characters. They also seem to sell marimo, but I have a feeling the little guys wouldn’t survive a trip that long.

Marimokkori!: So dirty!

Wendiland and eGardenStudio both carry marimo on Etsy: Go for it! They’re so cute!

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  • Reply pete February 23, 2012 at 4:10 pm

    Take a look at New Marimo Moss Ball water terrariums being offered starting today!!


  • Reply Finny March 31, 2012 at 11:43 am

    Sometimes the surface of marimo will get matted and dark like someone put mushed construction paper on it. Take a pair of tweezers or nail scissors and snip these off (while under water in a vase, its easier to see them that way and then rub the surface of the ball under water with your thumb. Don’t freak out if sudden it looks like its falling apart. Then put it in a new bowl/vase of water.

    😀 Sometimes I like to give my marimo a treat, they say you don’t have to have a current to keep marimo happy, but every once in a while, after their surface and squeeze bath, I will add an aquarium bubbler and airstone to their vase with a few drops of liquid fertilizer and let them roll and bounce around in the bubbles for a few days (like the week end). More surface debris will fall off and it will get some nutrients to the center of the ball so the center doesn’t completely die off and make your marimo weak.

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