BioGuard Smart Shock 1 lb s a multi-functional product that shocks, oxidizes, buffers, and clarifies pool water. It kills and prevents bacteria growth. This product has unique blue algae-fighting crystals that kill unsightly algae. There is no need to mix or pre-dissolve, just add it directly to your pool water. This product has also been proven to improve filter efficiency. Start swimming in as little as 15 minutes after application. Keep your pool water sparkling clear and brilliant looking with Smart Shock.