I thin as Gunnie said, polyp extension gives u a pretty good idea. When I have too much flow, my LPS retract and sulk for a day or so. If you have direct flow on SPS their polyps with retract and you can blow the skin off them. For my SPS, because I have constant speed cheapie wavemakers, I direct them toward one another a few cm's in front of my SPS. The flow patterns collide and become random and turbulent. Its best to work this out when u do a clean and the waters' full of crap, you can see how the water is moving. I have about 50x turnover in my tank, but the way it is setup my SPS get atleast that or stronger, and my LPS wave quite a bit but gently. I dont wana touch it now as they all look very extended and happy !