Yes I have no doubts you are correct!! Only thing is this doesn't need to be and can't be raked out. Just looks like heck. Is kinda strange tho the algaecide I put in didn't even seem to dent it. Should have at least done something if it is a form of algae. Problem is the FA is usually located around the edge in shallow water. But this is kind of everywhere depending on wind and direction. Hard to spray the whole pond.