The way I do it (gill_za's idea earlier in this thread) is to have the fan running constantly and the pump hooked up to the hygrotherm, so that it only circulates coolant to the rad when it needs to bring the temperature down. Not only is it a clever way to do it, it also allows the cooler time to bring the fluid down to a colder temperature before the hygrotherm kicks on again. You could just hook the pump up to your power strip and have it run constantly, but then you'd have no way to control the temperature automatically.
What do you mean by weird air movement? Are you saying the fan isn't pushing enough air? What fan did you end up getting (how many CFM) and how is it positioned in the tank?