Ok I saw both the mp20 and mp40 in action tonight...
The mp40 was in a Red Sea Max tank
The mp20 was in a 40 breeder
In both instances we moved the pump so it resembled a situation closest to my tank.
I think the mp20 would be good for my size tank if I was operating in any mode other than short pulse pumping a wave. IMO the mp20 just doesn't throttle up enough to get the job done. We had the RedSea Max rocking with the mp40 though! :lol:
Also, I was really surprised with the level of control on both powerheads, how easy the pump is to operate, and how easy it was to dial in the wave with the mp40.
That being said, I was very impressed with both units, and neither put out any audible noise at the rates I was cranking them. Also, I was extremely impressed with the massive undertoe these things create. There really was no area in the tanks not receiving some type of flow.
I think I'm going to go with the mp40 though... better to be safe than sorry, and I can always dial it down if it proves to be too much.
Thanks Mike and Sagi!