Can someone help me ID this ... organism on the glass? I'm talking about the crescent shaped object on the glass. At first I thought it was just algae but after observing them they have these thread like projections at each end of the crescent shape. It can extend and retract these threads possibly to filter feed? When they show up on rock work the almost 'stand' at the end opposite where the threads are. I have several on the rocks, but they seem to just wipe away off the glass fairly easily.