Iron stains are on 75% of saltwater pool (10,000 gal pool) bottom and have been there 5+ years, sort of like amoeba shaped with no definite edges. Used the AA treatment to try to remove stains. I took the chlorine down to 0, and ph down to 7.1-7.2 . Added 1 lb. of AA and let pump run 24 hrs straight. Added algicide also. There was some lightening but not much. The next day added another 1 lb. AA and sequestrant and let pump run 24 hrs. Couldn't see much success except there are now some visible "streaks" where some stain removal occured going toward the bottom drain .
The next day I added 1 lb of Suncoast Iron and Cobalt Remover. There was some more lightening after letting this work for 24 hrs but almost entire stain still visible (lighter than before I started though). Let run another day then added 1 1/2 gal Chlorine to return pool to normal.
Is there any reason the AA treatment didn't get rid of all stains? Did I do something wrong? Since it lightened them about half way, why not total removal?