Cocoons on Live Rock?


I have a 125 FOWLR set up approaching two years. Within the past month or so I started seeing what looked like small tufts of cotton. There's 3 or 4 of them and they are about the size of a nickle. They look kind of like the cocoons you see in trees that contain Tent Caterpillars, except they are under water. Any idea what they might be? Could they be fish eggs? I have several cleaner shrimp who have been in the tank almost one year. Do they lay egg? Anyway, does anyone have any idea what this might be? Thanks