Effective chemical concentration of the active ingredient of a herbicide needed in water to control the weed. The total amount of active ingredient divided by the total amount of active and inert ingredients. The herbicide label should be read and fully understood prior to pond application. Copper sulfate is primarily used to con-trol algae. It is a contact herbicide and quickly kills sensitive algal species.
Copper can interfere with gill function and if improperly used can be toxic to fish.
The majority of fish kills due to copper sulfate treatment are primarily caused by a massive algae kill and sub-sequent oxygen depletion problems. The effectiveness and safety of copper sulfate is determined by alkalinity and water temperature. In waters with an alkalinity 50 ppm, the rate of copper sulfate needed to control algae can be toxic to fish. Treatment at water alkalini-ties of 20 ppm is extremely risky. The toxicity of copper sulfate to fish increas-es as water temperature increases.