Aluminum Sulfate is a product better known as Alum. Alum is a white powder that when circulated in your swimming pool water, quickly clumps all the fine particles in your cloudy water, including green algae, into particles large enough that the green algae sinks down to the bottom of your swimming pool, clarifying your pool water. Then you simply vacuum the bottom of your swimming pool and all the green algae in it to waste. We do not recommend using Alum in pools that have Cartridge Filters. You may have noticed that we stated we know a “guaranteed” way of clearing your swimming pool water of cloudy water and green algae virtually overnight. We say this because every time we have used Alum to clarify our swimming pool water it has worked perfectly and consistently. No other flocculent we have tried has come close to matching the performance or consistency of Alum at clarifying our swimming pool water and clearing the green algae out of our swimming pool. Also Alum does an excellent job of removing the phosphates that algae feed on. This will help prevent new algae from getting a toe hold in your pool water. No food, no algae. To help in preventing new algae from getting established visit our site for Algae Bar. Alum lowers garden soil pH which helps garden plants such as hydrangeas, azaleas, rhododendrons, blueberries and strawberries.