Helps control algae growth in ornamental water fountains. Controls algae growth in ornamental water fountains. Helps clear cloudy water. Also great for preventing algae growth.Details: Not recommended for use in fountains with live plants. Could be hazardous to humans and domestic animals.For best results, place Fountain Block in direct circulation where water is active. For regular maintenance, replace block when fully dissolved (usually in 2-4 weeks) or as water begins to appear cloudy and/or green. One block treats 50 gallons.