Check the listing for details. Sirona Spa Care Defend - 2 Pack. Condition: New. Listed at 55.98 USD. Sirona Spa Care Defend is a specialized liquid blend of organic polymers. It's formulated to remove and prevent stains and scale buildup in spas and hot tubs, compatible with various sanitizers like bromine, chlorine, ozone, minerals, and biguanide. Product Features: Defend hot tub descaler is compatible with all sanitizers Removes scale and helps prevent precipitation of dissolved solids for beautifully clean results Defends against scale formation using a unique blend of organic polymers for soothing, mineral-free spa water Add this hot tub descaler to your spa water weekly for continued scale protection Sirona Specialties maintain restorative spa water and transform every spa into a soothing sanctuary Dosage: For spas up to 800 gallons, use 2 fluid ounces Sirona Defend. For spas over 800 gallons, use 4 fluid ounces of Sirona Defend. Use this product when water is cloudy. For best results, use this product weekly. Add recommended dosage directly to the spa.