The presence of excess copper ions in water is inimical to a number of aquatic organisms, including algae, plants, mussels and clams, and has a long history of use in marine antifouling coatings. McMahon and Tsou (1990) note that copper is relatively lethal to zebra mussels, with 5 ppm copper ions for 24 hr giving 100 percent kill of veligers.