Marimo Moss Balls Review

by Lisa Shea

It’s interesting that there’s even a problem with fake marimo moss balls. It shows the strange world we live in. I did tests and the Marimo sold by Aquatic Arts seem to be wholly authentic. Plus, they are awfully cute and enormously helpful to a fish tank.

First, some of the basics. MARIMO ARE NOT PLANTS. They aren’t moss either. They are algae which naturally can form into a sphere shape based on water wave action. In your tank you replicate that by turning them occasionally. That helps them to continually grow out in that sphere shape. They need gentle light and some nutrients (nitrates, carbon dioxide, etc.) to live. You’ll want to do regular water changes, just like with a fish tank. They live fine in freshwater but not saltwater.

With this set from Aquatic Arts you pay for 5 1-inch marimo. I got 7 in my package. If you look at other peoples’ 1-star reviews they complain because their marimo were damaged in shipping, probably by being shipped in weather which was far too hot or cold. That’s outside of the vendor’s control, and the vendor is awesome at replacing these problems. But the very fact that a small portion of marimo die due to those temperature issues in shipping means of course THE DARN THINGS ARE ALIVE. They aren’t plastic or fiberglass. Plastic wouldn’t get black and stinky due to overheating.

Still, what if it was moss wrapped around a foam core, as some unethical vendors do? The easy way to test that is to cut one in half. So I did that. As you can see, it is marimo algae all the way through. If it was wrapped moss it would then unwrap. If it was squished moss you would see the spaghetti-like mish-mash in its center where it was squished. Instead, this marimo has the nice radial growth shape from a center point. Again there is no “core” on a marimo. They don’t form around an object like a pearl does. They just grow out. So this is a real marimo.

Make sure you thoroughly rinse and squeeze your marimo when you first get it, then sit it in cool water for a half hour, then rinse and squeeze it again. Now put it in your tank. If you do get one that was damaged in shipping and is smelly, brown, black, etc., just contact them. They’ll send you new ones. If your location is experiencing a 110F heat wave now is probably not the time to order one via the mail.

Over time you can weigh and measure your marimo to watch them grow. That’s of course another sure sign they are alive. Just be patient. They only grow 1-2cm a year. On the other hand, if you see single strands reaching up toward a light, that’s a sign you got a moss-rolled version. So far, I haven’t seen that happen with these. And, again, I’d be able to tell if it was moss (rather than algae) when I cut one in half.

To summarize – these are absolutely perfect for my 20-gallon tiger-barb-only tank. The tiger barbs love them, the marimo help hold down nitrate levels, and they look cute.

Ask with any questions!

Buy these from Amazon: Marimo Moss Balls

Marimo Moss Ball – Fake or Real?

Marimo Moss Ball – Fake or Real?

by Lisa Shea

The marimo moss ball is one of the coolest additions one can get for a freshwater aquarium. But how can you tell if your marimo is fake or real? Here is how to differentiate between the real, healthy marimo moss ball and the fake moss or plastic versions.

To begin with, despite its name, the Marimo Moss Ball IS NOT MOSS. It is not a plant, either. It’s algae, which many people consider to be separate from plants. The way algae work is different from plants. So what you have is a form of algae that naturally grows out into a ball shape due to how it’s tumbled and moved around by water currents.

It needs gentle light to live, along with carbon dioxide and a few nutrients like nitrates. That means a marimo moss ball does delightfully well in most freshwater tanks. Goldfish will try to eat it, but most other fish will leave it alone.

One of the most common ways unethical vendors make marimos is to use actual moss rather than the marimo algae. They wrap that moss into a ball either around a foam / Styrofoam core to give it shape or just mush it into a ball and hope it holds tight. So the best way to tell if your marimo is real is to cut one in half. Here I bought seven of them so I didn’t mind turning that into eight by slicing one in half.


This is what you should see. No foam or plastic in the middle, clearly. A marimo has no “core” to it. It should be green right to the middle. And if you look, you can see a radial form to the growth. Things are oriented around that center. With a fake mashed-up moss one, it would look like swirls of random spaghetti in there as the fibers were all mished and mashed together.

Marimo are very hardy. You can’t tell if it’s real just by putting it in the sun for a day or yanking at its green edges. If you really wanted to kill one, you could fill a bucket with chlorine and drop it in there. That would do the trick. But you shouldn’t have to go to that extreme. Cut one open if you’d like. Then put them in your tank and see how they do. They should grow a centimeter or two a year. They should need some rotation to stay green on all sides. They should have a small effect on nitrate levels. They are, after all, living creatures.

Ask with any questions about your marimo pets!

Marimo Moss Ball Care Tips:

  • When you first get your marimo, rinse it thoroughly and squeeze it thoroughly. Then let it sit in cool water for a half hour before introducing it to its tank. Give it a final rinse and few squeezes, underwater, as a final cleansing step.
  • In the tank, make sure it has gentle light for a portion of the day. Make sure you do weekly water changes just like you would do for any tank creature. If it’s in a fishtank, this should already be taken care of.
  • If it’s in a fishtank, it already has waste to eat. If it’s not in a fishtank, give it a little food so that it has something to eat.
  • Rotate it every once in a while so a different portion of it gets the light.
  • Enjoy!

Buy these from Amazon: Marimo Moss Balls

Marimo Moss Balls Review