You are correct Tracy, usually Copper Sulfate of some sort. There are "Pond Dye"'s but no sence in putting a Dye in a pond that isn't around a house or bunch of Yuppies. That stuff wont hurt you unless you drink it. and its diluted so much that the bacteria in the water would be 100x worse for you. A good rule of thumb is that if you see dead fish or "Fish Kill" then dont go in or near the pond. Fish are hypersensitive to most chemicals and even the "Blue/Green" algae that is harmful to humans.