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Guest writer: Urusai_Uni#0007

Ever wanted a fun “pet” that was not only easy to take care of but looks cool too? Then a marimo might be just right for you! But what is a marimo and what does it have to do with Japan? In this article, you’ll find everything you need to know about marimo and the basics of how to start taking care of your very own!

All images, unless otherwise stated, are courtesy of Urusai_Uni#0007


What are Marimo?

Marimo, commonly called “moss balls” in English, are actually a rare type of algae formation! In 1898, a botanist from Japan named Tatsuhiko Kawakami named the balls “marimo”, mari being a type of bouncy ball toy and mo being a generic word for aquatic plants. This species of algae, under the right circumstances, can be softly rolled by the waves in shallow lakes, causing them to form balls. They grow about 5mm a year and can get up to 30cm (1ft) in diameter. They also can live to be 200 years or older!

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Marimo are fairly rare, only appearing in ball form in a handful of places such as Iceland and Japan! They appear in a few lakes across Japan, the most notable being Lake Akan, located in Hokkaido.

In 1921, marimo were designated a National Treasure in Japan, but they were still greatly threatened by things like development and also by stealing. Many people wanted to own a marimo, and they were often stolen and sold across Japan. Currently, Lake Akan is located within a National Park, and it is very illegal to take marimo from it. Marimo sold nowadays are grown in farms, although many of the ones sold to aquariums are from lakes in Ukraine.


Marimo as Pets

Marimo are popular as decorations or “pets” in Japan, although it is now easier than ever to get them across the world so their popularity is rising. They’re even available in some western pet stores that sell fish!

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Marimo can be kept either alone or in aquariums, although some types of fish, like goldfish, may try to eat them. I personally keep mine in different glasses and my favorite container I’ve seen them kept in was a glass teapot! Creating habitats for your pet marimo is half the fun of getting them!

As for actual care, they’re fairly easy. They prefer cool water and not too much direct light. If a marimo has brown spots, it most likely is getting too much sun and should be moved to a shadier place. A floating marimo is pretty normal as well and is caused by an air bubble trapped inside of it. It’ll normally go away after a day or two! Every two weeks or so, or if the container is looking a bit dirty, you should change their water and give them a gentle roll between your palms to help them keep their round shape. There’s no wave action happening inside a jar so simulated will have to do. That’s about it! They’re incredibly easy to take care of and add for a fun decoration to liven up a room!

Marimo can be purchased in a number of sizes, the most common being about an half an inch (1-1.5cm) in diameter, often referred to as nano size, and are roughly 5 to 10 years old. The largest marimo I own is roughly 2 to 2.5 inches (5cm) in diameter and could be over 15 to 20 years old!

A few of my marimo, ranging from less than 1cm all the way to my largest at about 5cm in diameter!



TThank you for reading and I hoped you enjoyed reading about this interesting creature! They make for fun and easy pets, a conversation starter, and bring you a little piece of Japan in a subtle way! Have fun creating the environment for your new moss ball friend and be sure to share what you’ve come up with!



Further Reading/Sources

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