Yeah, I never thought of it either until I started looking around at some other setups years ago. The external pump keeps the heat out of the water and gives you so many options! Whether you use a Hammerhead or another type of external pump, you can build a type of manifold that will feed everything. One pump makes it so much easier. Put ball valves on each output and regulate the flow you need to different areas. I think it is one of the best upgrades that I ever made to my setup. I've been running my Hammerhead nonstop for 4 years or so and I am very happy with it. I take it apart and clean it really well twice per year but is otherwise maintenance free.