Copper compounds, or precipitates, also settle out of solution, in a process called precipitation. This occurs less often than adsorption. Copper sulfate products should not be used to treat more than half of a lake or pond at one time, in order to avoid depletion of oxygen caused by decaying vegetation. The effectiveness of copper sulfate decreases as water hardness increases. As a naturally-occurring substance, copper can persist indefinitely.
Copper sulfate can kill plants by disrupting photosynthesis.
Skin should be washed immediately if contaminated, and work clothing should be changed daily if it is reasonably likely that it is contaminated with copper sulfate. Copper sulfate is blue and odorless. Copper sulfate is classified for shipping purposes as a hazardous substance or hazardous waste. Copper sulfate is highly corrosive to plain steel, iron and galvanized pipes. It should not be stored in metal containers.