Abstract: A medication mixing and holding tank having a medicated fluid outlet, a pump associated with the tank for pumping medicated fluid from medicated fluid outlet to a livestock watering line, and associated with the tank and pump and outlet recirculating line for agitating and recirculating fluid in the holding tank when no demand is made on the livestock watering line the unit dispenses substantially homogeneously mixed medicated fluid whenever a use demand is made on the livestock watering line. When all treating fluid is dispensed, the unit is automatically hooked into the fresh water line for continued dispensing of fresh water. The same tank is used for simultaneously mixing and metering.