I have a large area with discoloration and it is only on the shallow end 5ft and less. It doesn't come up with brushing so I tried putting a puck in, left it for 30 min and nothing, got in and scrapped it on the bottom and it didn't streak. Some kids were able to scrape their initials on the bottom so I tried the puck again left it over night. Next morning there was a circle, I know I left it to long but, does this mean its organic because I tried putting absorbic acid in a sock and scrubbing and it didn't seem to work. Would the puck do that if it was metals if left long enough?