The principle of this wavemaker was to have a low RPM motor spin a ball valve on the return line of the pump.  This would cause the ball valve to open and close thereby causing a surge in the return water.  In principle this would work.  The failure was that the ball valve began to leak around the shaft seal,  probably due to continous use/spinning.  In addition, the motor I picked up from a surplus place may not have been meant for continous duty as it would get very hot.  Someday I may come back and try to finish this idea but for now I have installed my solution.

Solution:  ReefRotor Wavemaker