RBC, it sounds like Cecil thinks so; since I've never used gypsum I don't know how to compare. An easy test: Go to the drug store and get a jar of alum (which is aluminum sulfate); get a couple of big jars full of pond water; put some of the alum in one; let the two sit and see what happens. If the alum one gets clarified, then aluminum sulfate will help. If you decide to use it, mix it up in a stock tank and add it throughout the pond. And if you can get it for $11/100 lbs by all means do so!!
