I've never seen any indication of the precise way a spray bar SHOULD be setup. That being true, whenever I've configured with surface agitation in mind (O2 injection). This, for me, meant mounting at the water line pointed slightly downward. Since I have configurable kit that allows for tons agitation, I decided to confure both of my bars about 2-inches below the surface and fire downward at a 45 degree angle. Why? Because the wife has quietly complained that the constant wash of the return is annoying. Opinions and knowledge on this subject would be appreciated greatly.