We are not the best pool owners meaning we do not check chemistry every week. I noticed today some dark blotches in some areas that would not brush off or even scrape away with my finger nail. I do not believe it any kind of algae. Attaching a few pics and wanted to get your thoughts.
Here is the link to the pictures of the pool. https://plus.google.com/photos/113694040658761970276/albums/6020051742175678929
Here is the link to the pictures of the pool. https://plus.google.com/photos/113694040658761970276/albums/6020051742175678929