There's a part of me that just wants to go to a smaller return pump, although it is reverse logic. In other words, let the return pump do what it is supposed to do -- return water from the sump -- and not be a supplement to flow. My Iwaki 30, even throttled down a bit, is ultra strong and pushes a pair of jets into the tank. I'd almost want it to trickle in... and let Tunze/Vortech provide FLOW to the tank.