I've been battling metal staining in my pool for most of this season. Ascorbic Acid in the form of vitamin C works well and so does Citric Acid (Natural Chemistry Stain Free for example) in removing the stains. The local pool store suggested 3-Met-0 Plus by Sani Marc (note 3-Met-0 is a liquid sequestrant, the 3-Met-0 Plus is a powder). The label mentions that it 'contains' Sodium Bisulphate. This video shows it doing an impressive cleaning job - http://www.youtube.com/watch?v=AUClby0bVGU
Does this stuff have any benefit or drawback compared to Ascorbic/Citric Acid? Does it consume chlorine like the Ascorbic/Citric?