Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants eat fish from copper treated pond?

Too much copper can be toxic and can cause a fish kill. Also, when you kill algae, the decomposition process consumes dissolved oxygen which can cause fish kills. General rule of thumb is 20lbs of copper per acre. If pond is 100% covered in algae, only treat half of it at a time, leaving about a week in between treatments.