You may make a wish when you throw a penny into a pond, but you're only creating illness for the fish that live in there. When you throw spare change like pennies and quarters into a fountain or pond, the copper inside the coins can harm the fish. The copper interacts with their blood cells and increases mucus production in their gills, which makes it more difficult for the fish to breathe and absorb oxygen. When they struggle to breathe, they gasp at the surface of the water for oxygen and ultimately could die. So if you want to make a wish, do so, but keep the coins in your pocket.
ANDREWS MCMEEL SYNDICATION