I had a Koralia 1 here (bought it for one of my nanos but never got around to taking it out of the box), and I put it in the 90g around 11am. My pavona, pocillipora and millepora retracted immediately. I adjusted the flow so it went more over than at the corals, and it made no difference. I unplugged it after a couple of hours, and even four hours later they had not relaxed enough to open up.

<sigh> I know I need more flow because I have to regularly blow detritus off my plating monti (top/center of the tank). I simply(?) need to determine what is best for my corals and the limited space that they live in.