Muddy water treatment calculator
Treat on a calm day and spread the product evenly over the whole surface, dissolved or slurried where you can. Do not treat when fish are stressed or oxygen is low. Alum settles clay for good only if the source of the clay is fixed: bare banks, livestock, a feeder stream, or bottom-feeding fish will muddy it again.
Method and sources
acre-feet = acres × average depth (ft); average is taken as 40 percent of maximum when not entered
One milligram per litre across one acre-foot of water weighs 2.72 lb. Without a jar test the calculator uses the extension ranges: alum 25 to 50 lb per acre-foot, gypsum 500 to 1,000 lb per acre-foot. Alum works at a fraction of the dose because it flocculates the clay rather than just settling it, but it also pulls pH down. When total alkalinity is under 50 ppm, add hydrated lime at half the alum weight at the same time to hold pH. Gypsum is slower and bulkier but does not move pH.
Jar test: fill a jar with pond water, add a measured small weight of product (a fraction of a gram per litre), stir, and wait an hour. Repeat with more or less until you find the smallest dose that clears the water, then enter that weight and the jar volume. The calculator scales it to the pond by the acre-foot. A jar test replaces the guess; the ranges are a starting point.
Sources: extension muddy pond sheets from Auburn University and Oklahoma State University. Practitioner discussion: Pond Boss forum threads Alum Kicks Clay Butt and Alum kicks clay's butt again.