Surge tanks are flow control devices, whose purpose is to smooth out the rate of change of flow of fluids passing from one process unit to another. Classical surge tanks controllers, such as PID, focus on regulating the volume of fluid in the surge tank at some 'safe' intermediate value, between overflow and emptying of the surge tank. There is interest, however, in alternative controllers which address more directly the important problem of avoiding excessive rates of change of output flow rate. In this paper, a differential games theoretic approach to surge tank controller design is proposed. Respects in which it improves on other non-classical approaches are discussed.