Giant Pregnant Marimo Moss Ball??!! How To Proprogate And Care For Your Marimo

1516046831080649593746-jl3yyylvkf.jpg 15157142806836419888-p81nll8pde.jpg 1515714679416571221788-4hc81u34oy.jpg Hey everyone, i thought I would write about the origination, care and propagation of the Marimo moss ball that so many of us have in our fish tanks. The top pic is my GIANT Marimo moss ball along with regular sized and smaller ones that I’ve propagated. The second pic is the same moss ball opened up a bit, trying to propagate, which it did on its own.

The Marimo is called a moss ball because it looks and kind of feels like moss while actually it’s an algae. The Marimo can be found in lakes in Japan and North Korea, I’ve read. There is algae in the lakes and that algae rolls around back and forth in the water and starts to form a ball and adhere to itself. They like cooler water, but can go up to around 75°. They grow 5mm a year, so pretty slowly. Marimo do not like direct sunlight, which can cause rotting brown spots, although fish tank lights are fine for it during the day. Indirect sunlight is ok if you are keeping one in a glass jar. The Marimos also need filtered water with no chlorine or heavy metals.

Marimo also have some great benefits for fish tanks. They add oxygen to the tank and eat up nitrates. They also house a good amount of beneficial bacteria. To keep your Marimo happy and healthy, you need to give it baths. Yes, I said you need to bathe your Marimo. To do this, you take a colander and put it in the sink. Then gently take the Marimo out of your tank, being careful not to squeeze out the water in the tank. Put the Marimo in the colander and run cold water. In your hand, take the moss ball under the water and gently squeeze it and rotate, squeeze and rotate. Do this a few times to ensure it is clean. Then squeeze it out again and return to the tank or bowl with filtered water. Also, from time to time play with your Marimo by moving it around so it changes positions. You don’t want to leave it in the same position on the bottom of the tank or bowl because this can cause rotting brown spots. However, if you do discover brown spots, just trim them off a little and put back.

Marimo, when it reaches a certain size or has not been rolled in the hand periodically, can have little pieces fall off. You roll them in your hand until a ball forms and now you have a baby Marimo! It will take awhile to adhere to itself, but eventually it will grow into a big Marimo. Another way to propagate Marimo is to pull off pieces to make smaller ones. Roll the pieces together in your hand and then wrap them in string to help them stay round and adhere to themself.

I hope I have taught you a little something about these fuzzy little fluff balls that have become so popular!

So... what do you think? Please leave me a comment.


  • Carley: Interesting! I’ve never owned a Moss Ball!
  • Amaris: They’re really cool!
  • Oreo1: So cool! I’ll have to try when I get home!
  • Vale: Why do you have to wash it? Is it to remove debris and fish / food waste?
  • Amaris: Well, yes to remove waste but even if you keep your marimo in a little glass jar as a plant and decorative object, you still have to bathe it. It needs clean filtered water, and can start to rot if not cleaned properly. If you keep your marimo in a jar of water you have to clean the marimo itself, and replace filtered water at least every 2 weeks to keep it healthy. When they are happy and healthy they get bright green! Especially after a water change as well! I know on here we think of them as moss balls to add to our fish tanks, but they are also kept as a plant, and pet almost. 😊
  • Amaris: Yes Oreo1, you can just open one of them up with your fingers and pull apart and make as many, as you want! Whatever size you choose! Be patient though, they take time to adhere once propagated, but definitely will in time. Just every so often roll it in your hands to keep the shape.
  • Vale: Thanks for the info Amaris! I read that the Japanese keep them for good luck too
  • BetterBetta: I never knew they could get "pregnant" or at least the way you showed. Thanks for this! Super Interesting
  • Oreo1: My moss ball made its own baby!!! 😳😳 woohoo!!!!
  • Amaris: Awesome! Thats cool Oreo1. In time it will grow a lot bigger.
    Ya, they aren’t actually "pregnant" but they do start to mimic it by letting off little pieces creating baby marimos.
  • Amaris: Yes vale, they do also keep them for good luck. More likely in a nice vase decorated with stones and things. They make very pretty plant decorations. I keep a bunch in a big bowl of water on my table, lol.
  • Vale: Nice :)
  • Amaris: Vale, i was wondering if you could take down the link that says the top pic is from filkr, because it’s my own pic?? Just don’t want any confusion, or it saying it’s someone else’s pic. Thanks!
  • Vale: done :)
  • Amaris: Thank you so much! Just want to show off my extremely over sized Marimo, lol.
    I’ve never seen one so big, even online. I has to have it when i saw it at my little ma and pa shop fish store.
  • Vale: :)

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