hd82, yu don't need to be that precise when it comes to applying Alum (AlSO4)

Got back to the pool suppy place and get a free water sample anaysis too. I'd like to know your alkalynity and total hardness. It sounds like you could benefit greatly from a few tons of Ag lime.

By the way, Powdered or granular Alum will both dissolve in clear water at a rate of 1 pound Alum per gallon. If using pond water, make it 1 pound Alum per 2 gallons of water.

DO NOT mix the Alum and Hydrated lime together....it forms plaster!