Pool Rx+ the advanced mineral based pool and spa tablet algaecide formula from the trusted Pool Rx brand. Pool Rx+ harnesses the power of three active ingredients: Copper Sulfate Zinc Sulfate and Silver Nitrate providing enhanced protection for your spa water. The yellow/white Pool Rx+ spa unit is EPA Registered and NSF/ANSI 50 Certified algicide making it a reliable choice for spas holding 100 to 400 gallons of water. With Pool Rx+ you can enjoy reduced chemical demand improved water quality and simplified spa maintenance for up to 6 months. Re-treatment intervals may vary depending on factors like bather load and splash out. For optimal results replace the Pool Rx+ spa/hot tub unit every time you drain and refill your spa/hot tub or if you notice the first signs of algae or dull-looking water even if your chlorine levels are within the 0.5-1.0 ppm range. Pool Rx+ products are versatile and can support any size spa whether you use Chlorine Salt UV or Ozone sanitizing systems. Upgrade to Pool Rx+ and experience a cleaner easier-to-maintain spa all season long.