So recently I saw some moss balls at the pet store, which I thought looked pretty neat for a tank. I have 4 pet minnows (I know, they're not tropical) in a 10 gallon tank with an aerator, a filter, small rocks, a couple big rocks, and some decorations. What I'm concerned about is that putting a moss ball in my tank could harm them in some way. Is there any chance, what so ever, that a moss ball could harm my minnows in any way?