Clorox Pool&Spa XtraBlue long-lasting, Chlorinating Tablets work hard to keep your water clean from both harmful bacteria and unsightly algae, while protecting your surfaces from stain and scale, saving you both time and money. Keep your pool beautiful with these weekly-use tablets. Each tablet dissolves slow and lasts longer because they are protected by sunlight. Can be used in a skimmer, feeder, or floater.