A method for controlling bivalve growth in a static or semi-static service water system of a plant is disclosed. Upon detecting an increase in the concentration of veligers or settlement stage bivalves, potassium is introduced into the service water to obtain a potassium cation concentration of between 10 mg/l and 150 mg/l for a period of 2 to 30 days. The methods are particularly useful for controlling zebra mussel growth in service water systems for fire prevention.
