Pool stores love to sell chemicals! That is how they stay profitable and in business. More chemicals only end up causing more issues down the road. Do you like purple stains in your pool? If so just dump in some of their super duper algaecide and the copper that kills the algae will also give you a nice purple stain. Another good one is you need to shock your pool. The last thing your pool needs is more CYA! CYA reduces the killing effectiveness of chlorine. It’s a scientific fact folks! There are defiantly a time and place for some of these products but the over use of them is rampant. Most times all you simply need to do is keep your water fresh and let the chemicals required in swimming pools work more efficiently.