In The Swim Metal Out Spa and Hot Tub Chemical - 1 qt.
Spa Metal Out helps eliminate iron and other metallic stains that can occur in spas.  Effectively disperses precipitated metals and other staining agents in spa water.  Can also be used to gradually remove an existing stain.  Dosage: 16 oz. per 500 gallons (maintenance) or 32 oz. per 500 gallons (stain-removal).