Keep your home clean with this 8-pack XtraBlue Clorox Pool and Spa Shock. It is fast dissolving and treats water quickly, leaving it safe for swimming within 15 minutes. It is easy to use and requires three simple steps, detailed on the package. This 1-lb pool cleaning shock uses special crystals to kill and control green, black and mustard algae to keep your system clear. It eliminates bacteria and breaks up cloudy water. It can even improve filter performance. This value pack is easy to open and pour.