We've had some brown stuff at the bottom of the pool that would come right back after vacuuming. I figure it's some kind of algae. I shocked the pool yesterday, had to add 7 of the 3 qt bottles of bleach to keep it at 15 FC. There's no CC. This morning I only had to add one. Should I continue to keep it at 15 today? This was an expensive shock! Also, I kept the vacuum running all night. Should I have done this? Thanks!