Wet & Forget Moss Mold Mildew Algae Stain Remover – Costco Sale! by Rhonda April 30, 2022 April 30, 2022 *UPDATE* 4/30/22. The Wet & Forget Outdoor Moss Mold Mildew & Algae Stain Remover from Costco is designed to make outdoor cleaning quick and easy. This bottle attaches directly to… 0 FacebookTwitterPinterestEmail