The first thing most customers will ask is if the chemical prescribed for treatment will harm or kill the fish. There could be many answers to this question, but if the chemcal is apllied in accordance with its label, no it will not. That is why it is important to hire qualified and responsible chemical applicators that use aquatic labeled chemicals. There are many varibles to applying chemicals in a body of water. Fish kills following chemical application are usually a dissolved oxygen issue from treating to much vegetation at one time. Rotting vegetation will burn up dissolved oxygen levels and fish will suffocate if levels get to low. When treating bodies of water that has a lot of submersed growth, applicators should only treat half to a third of the body of water at one time.