I have been keeping a duncan for a couple of months now, and it has been doing great. Grew from a single head to six heads in just 3 months, but a few weeks ago it quit extending as much, but still seemed to be happy. Now, it has completely closed up and has not been open for four days. I moved it to a lower flow and lower light spot in the tank, but does anyone have any thoughts? I have a zoa and another piece of coral in my tank that are both as happy as always, so I don't know that it's water chemistry related.