Excellent question, and one we get ALL THE TIME!

So let’s dive in.

Marimo are a unique, orb shaped algae that sink and float for two reasons: photosynthesis and the circadian rhythm.

In their natural habitat of freshwater (and occasionally brackish) lakes and rivers, Marimo photosynthesize, just like land plants. Oxygen is released as a byproduct of photosynthesis and the air helps to lift and keep the balls on the surface of the water where they gather light energy from the sun. Those tiny bubbles stick to the surface layer of filament. Did you know thousands of strands of filament make up each Marimo ball? Picture a ball of yarn with string wrapped round and round to create an orb and you're on the right track!

So that makes sense, they float to photosynthesize, but what other factors contribute to their seemingly mysterious movements? In recent studies, we’ve learned oxygen isn’t the only thing that makes these algae orbs buoyant! Like plants and animals, Marimo respond to the circadian rhythm.

What is the Circadian Rhythm?

Have you seen our time lapse videos? Over the years we've shared dozens of videos highlighting the movements of plant life that goes unseen in our day to day. Those houseplants are grooving to the circadian rhythm beat! Oxalis, maranta, monstera and calathea are all beautiful examples of how forces of time and light affect us all. In animals, the circadian rhythm is the internal process that regulates our sleep-wake cycle. This cycle generally repeats itself every 24 hours. But like plants (and algae), the circadian rhythm communicates the season, time and temperature of their surrounding environment. It also tells plants when to flower for the best chance of attracting pollinators and therefore, to survive as a species. 

So why do Marimo not sink or float in my home?

That’s where things become a little bit trickier! In nature, Marimo adjust to the natural rhythm of day/night light cycles. The sun comes up and they may rise with the sun while photosynthesizing, the sun goes down and they sink again to rest on the sandy lake or rocky river bed.

However, in our homes, we turn lights on and off throughout the day and into the evening, which confuses the natural day/night signals and therefore effects how and when Marimo sink and float. 

We've been curious to see if we could capture those sneaky movements to understand this concept better. In our most recent time lapse video, we kept an ambient LED light on in the background during the entire 12 days of filming. We weren’t sure how the Marimo would react but were thrilled to witness how capture Marimo indeed rose and fell a few times! We did add water to the vase one of those times, which increases oxygen levels in the water, but that doesn't account for the other two times we captured it surfacing! We'll add a link at the end of this post so you can see it too!

Did you know we created a digital natural science lesson featuring Marimo? We wanted to encourage more connection with nature and less screen time for families stuck at home. The first lesson is free!

Hope this helps explain why your Marimo may hang out at the bottom of the vase. That's right friends, you are not doing anything wrong if your Marimo don't float! If you want to experience more floating Marimo moments, you can change out the water more frequently and give your Marimo a gentle hug with two hands to clean and release some excess water before replacing it into the clean water. You can also add carbonated water to the vessel a few times a month to increase CO2 levels! We have a wealth of tips and tricks for you in our Community Resources pages here on our website too!