Ok I feel really dumb here. I am trying to clean tiles at the water line which seem to have a calcium buildup. I am using a pumice stone that I purchased at Home Depot in the pool chemical section. As I am rubbing off the buildup, the pumice stone is dissolving and going into the water. Also little pieces of the stone are breaking off and falling in. Is this supposed to happen? Am I doing something that will damage my filter or pump?