You might know that lead can be toxic, and that you can get lead poisoning from eating or inhaling old paint dust. Lead is called a heavy metal, and there are other sources of heavy metals that can be toxic, too. Silver, copper, mercury, nickel, cadmium, and chromium are all heavy metals that can be toxic in certain environments. In this experiment, find out if one common heavy metal, copper, can be toxic to an aquatic environment.