I read somewhere that sometimes "fake" Marimo algae are sold labelled as true Marimo. Those are just a ball of algae really similar to Marimo algae (Scientific name: Aegagropila linnaei \ Cladophora aegagropila). So the fake Marimos probably still belong to Cladophora genus, like the true Marimo, but they are a different and more invasive species.
I don't know if that's true. Another option could be that those people bought Marimo that carried some other algae on them. Then they didn't keep the Marimo ball in proper conditions, causing it to fall apart and disgregate, and at the same time the other "bad" algae took over the tank. Since both have similar structure, those people thought that that invasion was due to marimo ball hairs that came off. I think that only an algae expert could tell if those invasion of algae hairs belongs to Aegagropila linnaei or to another species.
I don't know if that's true. Another option could be that those people bought Marimo that carried some other algae on them. Then they didn't keep the Marimo ball in proper conditions, causing it to fall apart and disgregate, and at the same time the other "bad" algae took over the tank. Since both have similar structure, those people thought that that invasion was due to marimo ball hairs that came off. I think that only an algae expert could tell if those invasion of algae hairs belongs to Aegagropila linnaei or to another species.