I've got the same dilemma and I'm probably going to setup an air pump and air stone to agitate the surface of the water in the sump a bit. I just need to find an air pump that isn't too noisy.
tannable75 said:Instead of adding more equipment just to move the water in the sump more, you could redirect a little of the return water with a gate valve to go back into the sump instead of the tank and position this in such a manner as to maximize surface movement in the sump.