Xenia and Flow

Hi guys, I have a two part question. Recently i bought a small xenia frag, and noticed that he seemed to be getting beaten around pretty good by my MP40 and MP10 (which were cranked right up), therefore causing him to not open. I moved him to a few different locations in my tank but nothing's changed. I turned down my powerheads a great deal to slow the flow for him but this then begs the question, how much flow is too much? I want to keep the tank disturbed but not kill any corals in the process. Possibly the flow wasnt the issue and he's refusing to open for other reasons? Water parameters are:

S.G.- 1.026 phosphate- 0ppm
Ammonia- 0ppm calcium- 480ppm
nitrite- 0ppm dKH- 9
nitrate- >5ppm Magnesium- 1420ppm
pH- 8.0 avg.