Noticed the first couple days after my new pool was finally filled a few stains in the pool. After reading this forum I was more concerned and had my water tested for metals which was 0. I got one of those erasers from Leslie's and rubbing lightly on my new black bottom plaster seemed to remove it although it did leave a mark on the plaster. There are a couple more about a dime size and one of the more darker one looks like its missing plaster about a BB size in diameter and about the thickness of a DVD if that. I didnt want to rub it with the eraser not knowing what further damage it may cause so I have been monitoring it for the past week now. Salt is goign to be added in a few weeks.