In July of 2012, I applied Power Plus Powder shock directly to my pool (Gunite pool). However shortly after it was applied we lost power for approximately 12 hours. When I checked on the pool the next day there were dark stains on the bottom where the shock laid on the bottom. I have still not been able to remove the stains.
For approimately 2 months before this I was using a weekly dose of Copper Algaecide for maintenance as well (left over from the opening kit).
From research it sounds like this could be metal that has attached to the pool itself, however a couple treatments of Metal Out did not seem to have any effect on the stains.
Is it possible that this could be some kind of stain cause by the shock sitting on the pool bottom for such a long time?
I plan on using a regular treatment of the stain remove in the link below to see if this provides any results.
http://www.lesliespool.com/Home/Pool-Ch ... 14222.html