One of the most important steps to the Aqua Silk Chlorine-Free pool care system is adding Aqua Silk Algaecide. This powerful algaecide is effective against green, black and mustard algae as well as unsightly slime deposits. Useful Tips: Kills and prevents algae, improves filter operation and reduces the need for other chemicals, Add directly to pool water. Compatible with Aqua Silk Pool Care System products. - 12 quarts per case