Alum is most often used at 25 to 50 pounds per acre-foot of water per treatment with fish present. The number of applications needed will vary depending on the concentration of suspended clay or algae particles.

Your first treatment should be made at the rate of 25 pounds per acre-foot. Clay particles should settle and the water should start to clear within a few hours after application.

Alum can reduce the pH and alkalinity of pond water due to a strongly acidic reaction in water, so testing your alkalinity and pH before and after your first application will help you determine if you may need to buffer your water using something like hydrated lime or sodium bicarbonate. Additional applications can be made at 25 - 50 pounds per acre-foot as needed.

For small ponds, we recommend dissolving the granular aluminum sulfate in two or more gallons per pound in an IBC container or any other large plastic container, since aluminum sulfate will corrode metal. Be sure to rinse your equipment well. Once the alum is fully dissolved, a sump pump and garden hose can be used to spray the solution from a boat or from the banks.

In larger ponds, a dissolved solution of alum can be poured into the outboard motor wash of the boat.