Plant of the Day Marimo Moss Balls Cladophora aegagropila/Aegagropila linnaei

Posted by Ruth McDonald on

Let's be clear, these are not moss balls. Marimo is a type of algae and can form a sheet that you can tie to wood of rocks, or under special conditions will form balls. Cladophora balls used to be found across Europe, including parts of the UK. But sadly pollution, mostly agricultural runoff has driven them to the extinction in many places in Europe and other parts of the world. 

 Why they grow in balls isn't clear, with the leading theory being that it allows more algae to grow in a small area. The how involves gentle rolling on a soft sandy bottom of a lake or similar, where the water is either deep or has something stopping strong light reaching the balls. These balls are hollow inside, and during periods of strong light can fill up with oxygen and start to float. In the wild might, the science is unclear, leads to the death of the algae as when they are exposed to strong light they start to die. Equally, they need a significant amount of light to photosynthesis, something that means that pollution leading to heavy blooms of other algae, and sediments being disturbed can kill off these balls. 

 Iceland is among many nations that are now scrambling to save their lake balls. Check out this article about the story of one lake and the moss balls that are now possibly gone.  But Japan has had a century of protecting them as a National Treasure, and their wild stocks are thriving. 

 So where do the moss balls we have in our tanks come from? Mostly still out of the wild sadly, but the larger growers take a small number of moss balls and break them down into smaller amounts to grow a large number of balls without stressing the wild stocks. The vast majority of wild-collected moss balls come from Lake Svityaz in Ukraine. 

 Why would you want them in your tank? Like all algae, they will help soak up some nitrates, but don't give them too much, or expect them to be a good replacement for water changes. If allowed to grow wild they will fill a tank full of filamentous algae. 

They are not a tropical plant, so avoid them if you have a tank that is at the top end of tropical. 

 They are revered in Japan and loved in many countries. So if you do get them for your tank enjoy this fuzzy little ball with a rich history, that is struggling in many places, but is the reason for many lakes and rivers being cleaned up. 

Did you know that Aegagropila linnaei the algae in these balls is still found in rivers in the north of England? Maybe one day our own lakes will have lake balls in their depths again. 




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