They tend to extend more in a moderate flow. A real strong flow and they will retract slightly. This doesn't mean they are unhealthy, I just think it keeps them from being buffeted around. I have target fed mine meals as large as krill, but it isn't really necessary. They are photosynthic and can also catch food when you feed your fish. I don't think they need pristine water. As a matter of fact, most of my LPS have done better in higher jutrient water. They don't seem to do as well in my tank designed around SPS.
Basically its a good hardy beginner stoney coral in my opinion.
Mike