JMAC - we have never mixed Copper Sulfate with any other chemicals for algae treatments so I can't speak from expierence on interactions that may occur. I can tell you that we had a fish kill once using the "crushed powder" form of copper sulfate, it basically dissolved too quickly in a very small area and caused a localized DO sag. If you are going to use copper sulfate, which I would not recommend in the first place, I would make sure that you buy the large crystal form that dissovles much more slowly in the water. Over the years we have used the crushed powder form, and both the small and large crystal forms. It is effective on algea blooms and FA but on other types of aquatic vegetaion by itself it is not very efffective even in the early stages of weed growth.