Hi!
I just thought I'd share my experience with Duncans.
When I got mine it was a little 2 headed frag and for the first few weeks it was shy and rarely opened. I was a little worried but it just seems like these corals take a little longer to get used to a new system than other corals do. In the beginning I had success seeing it open when I put it in a shaded spot and now its perfectly happy out in the open under the light.
Once they are used to their new environment I began target feeding them by squirting some mysis and brine over them and once and a while hand feed one of the polyps a piece of krill.
In just a few short months it went from having 2 heads to having 6 heads!