I've got three Acans and one Duncan and I don't target feed although I have occasionally in the past. Whenever you feed your fish these types of coral are bound to catch some of the missed scraps which is good enough for me.
Here are my results without target feeding. The colour hasn't actually changed, I just did a better job with the camera.
January 1 2011
January 7 2012
I also grew this colony from three polyps. This picture represents about 3 years of uninterrupted growth.
