Little has been studied on the affects of copper sulfate concentrations on many of the large number of species of zooplankton and other micro invertebrates including protozoans, rotifers, and not even considering affects on bacteria. IMO the srac.tamu FactSheet noted above is outdated and was based on too few old studies that examined copper effects on larger common test invertebrates and fish. Dissolved copper ions are toxic and the smaller the organism the more toxic it becomes. As noted in the SRAC fact sheet alkalinity and hardness play a big role of coppers toxic effects because the negative carbonate radical binds with the positive copper ions reducing its reactive concentration thus minimizing the toxic affects on non-target organisms. Low alkalinity allows more of the copper ions to be reactive and absorbed.