Check the listing for details. Rx Clear Stain Off Removes Stains from Swimming Pools - (Choose Quantity). Condition: New. Listed at 19.92 USD. Rx Clear® Stain Off 1 lb Swimming Pool & Spa Chemical For Brown & Black - (Choose Quantity) Rx Clear® Stain Off is recommended to help remove brown, grey, and black stains from the surface of your pool. Works on all pool surface types. 1 lb per 10,000 gallons of water. For removal of brown, grey or black stains from fiberglass pools & spas Also works on marcasite & vinyl swimming pool surfaces Active ingredient: ascorbic acid 100% Features: LIKE NEW FINISH – Impress your family and friends alike with the like-new feel of your aged swimming pool! Improves surface quality appearances and deeply saturates long-lasting stubborn stains with ease. KEEP CONTROL - Prevents stains, scaling, and brown water due to mineral buildup. Rx Clear Stain Off helps control iron levels and the levels of other metals in pool water. HIGHLY EFFECTIVE - Rx Clear Stain Off, is recommended to help remove brown, grey and black stains from the surface of you pool in a quick and timely fashion. EASY TO APPLY - Compatible with all sanitizing systems, Rx Clear Stain Off works perfectly on vinyl liners, fiberglass and even metal surfaces. This product is user friendly and fights both specific stained areas and problematic water discolouration.