Originally Posted by NorthernLights
Okay, so pardon my lack of understanding here...
Is there any downside to keeping a marimo ball in a tank?
The only downside I've seen is that I have a super aggressive fish. He attacks anything that moves. As aokashi said marimo moss balls float when the light is turned on and sink when it's off. Well... my fish decided that he wasn't going to tolerate the floating thing in his tank and completely destroyed it. (I was picking out marimo bits for weeks from his tank.)
Other than that I have not seen a single downside. They're so cute and my other fish loves to poke at his with his nose.