BioGuard Smart Shock is 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, add it directly to your pool water. Improve filter efficiency with BioGuard Smart Shock. Start swimming in as little as 15 minutes after application. Keep your pool water sparkling clear with Smart Shock.