I get these 1/4" long dark things the diameter of pencil lead on my deck that blow in the water and make a dime size orange spot on the bottom of the pool. They seem to come from under the edge of a maple tree. I believe it to be some kind of insect dropping but I'm not sure. Some days I get dozens of them and they look terrible. The spots don't clean off but disappear on their own after a day. Any ideas what it is or how to get rid of it?