Halimeda (cactus aglae): magic macro-algae
The green stuff in this picture is called halimeda and is a type of macro-algae. It's commonly called a cactus algae because of its resemblance to certain types of cactus. I'm not going to get into the deep details, if you are interested then you can read more elsewhere. The point of this article is to talk about the benefits to your tank.
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