Kramnorreh

I have a 17,500 gallon fiberglass pool and was using a copper based algaecide for maintenance 2oz every week. It started raising the copper level in my pool and ultimately stained the pool and some white fittings. I had never seen anything like this and thought it was black algae. So of course I added even more copper algaecide that made it even worse. Finally I was told to check for stains by buying some vitamin c tabs and drop a few in to see what effect it had. It was magic so then I read about citric acid and proceeded to put 10lbs in my pool. Got rid of every stain plus chlorine and lowered ph to 6.2. Needless to say I had to put my pump in one end and hose with fresh water at the other end. Things got back to normal about 18000 gallons lit's own. Of course then had to redo salt, cya, and ph and alkalinity returned to normal own its own. Finally started holding chlorine. Now I know. Should have tried 1 lb. of citric acid. It was a real pain. Know what you are doing before jumping into this for stains