Hi from Michigan and I just opened up pool late last week on my 4 year old salt water gunnite pool and I have some major ugly stains and am not sure the best way to attack. I think we have ruled out that it is not an organic algae stain as we have shocked pool to a ph level reading High (9+) and it did not loosen anything up. All other tests are not working as im trying to reduce ph level to a spot where the tests can work. What I can say is that after leaving a few vitamin c tablets on a stain for about an hour that the st
ain seemed to lighten in the spot where the tablets sat. Any help would be most appreciated. Thanks
ain seemed to lighten in the spot where the tablets sat. Any help would be most appreciated. Thanks
If Vitamin C tablets remove the stain, they are from iron. Are you on a well? Regardless, the pH should never be in the 9 range, so if you haven't lowered it yet, make that a priority for sure. If the staining is iron, an elevated pH and high FC level will only aggravate the iron and make the staining worse. See the link below for more details. Also take a look at our 
