My wife and I recently purchased a home with a "pond" in the backyard which was once a pool. It sat full of rain water for almost two years until we recently pumped it out with a sump pump, hosed the walls and added the proper chemicals to get it back to being a pool. However, after several months of shocking and keeping the water at the proper levels we are still noticing staining on the walls and what I'm assuming is scale. Before I go jumping into metal cleaners and stain removers I thought I would check on here to see if anyone could better help identify what the staining may be and any possible solutions there are to help get the pool looking better. The dark spots on the wall did have some sliminess over it and I've kept the chlorine at shock level until the FC no longer dropped overnight. I've also brushed the walls at least once a day. The stains however have seemed to stop dissipating any further. Any help you could provide would be greatly appreciated.