|Aquadex 50 Stain-Off / Spa Stain Off removes copper iron and metallic stains from plaster pools and black colbalt stains from fiberglass. Stain removal results can be noticed within 48 hours up to 10 days depending on how old or fresh the stains are. The product is stable at higher temperatures so works well in the spa environment. The effectiveness of Aquadex 50 Stain Off wonâ€™t be compromised by chlorine, acid or other sanitizing products. The product can be mixed with Plaster White â€˜n Brite as a booster for removing difficult metal stains in an acid wash.