I am getting ready to close our pool. I had it plastered this summer by Anthony Sylvan. I live in PA and it is still 70 during the day and 50 at night. I left the pool get away from me a bit and it got dirty and algae grew on it in some places. I shocked it and brushed the walls repeatedly and it is pretty good for the most part except there are some light algae areas yet that don't come off with the brush. Plus this year with the new plaster I noticed a weird kind of algae that I had never seen before. They are nearly black little round circles, smaller than a dime mostly, that don't really seem to go away after I shock it. You can dive underwater and really scrub at it and it kind of goes away. My question is can I cover up the pool now and deal with it when I open it next year or should I get rid of both of these algae issues now. I am afraid the algae will stain the plaster over the winter under the cover. Below is a picture of both types of algae.
[attachment=0:2vz5cnbf]Black Circle Algae.JPG[/attachment:2vz5cnbf]