Marimo Moss Balls - Care

Marimo "moss" balls aren't moss at all. They are actually a type of algae that slowly spins underwater to form nearly perfect spheres. When I think of marimo, I think of them almost as the plant version of the “pet rock” - it kind of just sits there, growing at a snail’s pace of 5mm per year. But, that doesn’t prevent them from being fascinating.

The Story

Found in Lake Akan and according to Japanese myth, marimo are the result of a poetic love story: two forbidden lovers running away to live in the woods where their spirits transformed into “moss” balls in the lake, living together forever.

Natural vs Farm Raised

Marimo (Aegagropila linnaei) are a protected species in Hokkaido, where Lake Akan resides. Marimo Matsuri is a festival that educates on their conservation. Thus, many of the balls we buy are likely farm raised.

According to MossBall.com, the way to tell natural from farm-made is to divide the plant. Natural marimo have a neat radial inner structure, where as farm-made are more randomized.

You can buy marimo online and locally, you're likely to come across at a pet store but some boutique plant shops may have them.

Plant Care

Light:

Medium light: absolutely no direct light as it may scorch the plant. They can tolerate low light as well.

Temperature:

Cool water, mimicking their native habitat. This is especially important during summer months where indoor temperatures are warmer.

Changing the Water:

I use regular tap water without issue, changing the vessel every 1-2 weeks. I like to squeeze my marimo gently under a running tap to excrete old water and replace it with new. This also helps get rid of air bubbles that may cause floating.

Troubleshooting

Dividing marimo moss balls in bowl with fresh water

Browning:

This can happen if the marimo is not getting enough light or needs a water changing (sometimes both). You can leave minor brown spots, or trim them away if they don't resolve with proper care.

Whitening:

Is often because of too much light: move your marimo to a more shaded location.

Mushy:

If your marimo is soft, squishy and has a pungent odor it's likely rotted. You can trim what you can off to attempt to save it.

Propagation

Dividing Your Marimo:

Propagation by splitting is as simple as gently prying the ball in half. Roll the newly divided mass (like a dough ball) and continue to agitate the water regularly. Realistically, your divided marimo will stay lumpy without regular movement. Consider it personality.