I am going to use one powerhead for the wave affect, I have been plugging and unplugging it for the time being to "test". =) I have a nice rotation current established with one of the penguins, the power sweep (which nolonger sweeps =( ) and the filter, basically the current goes up the right hand side across the top down the left hand side and across the bottom. Then I have the other penguin powerhead crossing this path going from back to front at the top of the aquarium, even with the pump on continually it causes some cool swirling currents.