Copper sulfate pentahydrate is a fungicide However, some fungi are capable of adapting to elevated levels of copper ions. By mixing a water solution of copper sulfate and a suspension of slaked lime one obtains the Bordeaux mixture, a suspension of copper(II) hydroxide Cu(OH)2 and calcium sulfate, which is used to control fungus on grapes, melons, and other berries.
Cheshunt compound, a mixture of copper sulfate and ammonium carbonate, used in horticulture to prevent damping off in seedlings. Its use as a herbicide is not agricultural, but instead to control invasive aquatic plants and the roots of plants that may be situated near pipes containing water. It is used in swimming pools as an algicide. A dilute solution of copper sulfate is used to treat aquarium fishes for parasitic infections, and is also used to remove snails from aquariums. Copper ions are highly toxic to fish, however. Most species of algae can be controlled with very low concentrations of copper sulfate. Copper sulfate inhibits growth of bacteria such as Escherichia coli.