I just set up my new tank and I wanted lots of flow...So I had 2 pumps (one for each side). Right now, I only have one running.
What I found, I was pushing so much water that my refugium was in so much turmoil, it wasn't a place of refuge for anything.
So, I am doing just like Ryan suggested. The return pump is for the filtration. Power heads are used to create the extra water motion in the tank.