The pool company, nor I know what this stuff is. Can someone help me identify it and treat it? It grows in circles and rectangles under the water line. Look under the water in the pictures and you can see it. The fiberglass pool is new and the peagravel hasn't been removed from it yet so don't mind the mess sitting in the bottom of the pool. Thanks for your help. We'd really like to get the mess cleaned up before we winterize the pool for the year.

Thanks
Jon
100_1543-1.JPG

100_1544.JPG

100_1545.JPG

100_1546.JPG