Multi-functional shock treatment for weekly use Prevents bacteria & algae Use weekly to solve 90% of pool water problems within 24 hours Restores crystal clarity in 24 hours Visibly brilliant sparkle This Cal Hypo based formula sanitizes without adding cyanuric acid (CYA) to prevent over-stabilization or chlorine lock. About HTH® Pool Care HTH® was developed with the pool owner in mind. We know that maintaining your pool water can be a lot of work. That’s why we're here every step of the way, helping you clear the uncertainty from pool care. With economical, easy-to-use solutions, HTH® is designed to work hard so you're prepared to tackle whatever life throws in your pool. From balancing your water to treating green water, we offer a full line of products to keep your pool water healthy and your swimmers happy. Stay all clear for cannonballs! This fast-dissolving, convenient 4-in-1 formula kills bacteria and algae, reduces chlorine odor and irritation and quickly restores crystal clarity. Compatible with all swimming pools This product is great for all pool types including vinyl-lined pools and salt water systems. You're all clear with HTH® For best results, use with HTH® 6-Way Test Strips to test and balance your swimming pool water twice weekly.