I started a new tank about two months ago. Today i started cleaning the glass on my tank and while doing so i noticed dozens of translucent "flaps" "crawling" along the glass. ranging in size from about 2-5 millimeters. I tried to take pictures but they were too small and clear to come out in them. So all i can do is describe them best i can and hope someone knows what they are. the front end, when flattened seems to be saucer shaped and slightly wider then the rest of the animal, with a small orange dot being the only color, and it seems to be inside the animal towards the center of the front. the tail end is slightly more clear and shaped like a crescent moon with two points pointing away from the animal and curving towards its body in the middle. they seem to be eating the algae off the glass but i can't be sure. I don't know if they're all just baby something or just a smaller creature, but with the amount of them i noticed overnight I'm leaning towards young. can someone tell me what this is.. if its harmful to my tank or if i can just leave it?