It depends a lot on what type of Gorgonian you have. We have 2 kinds of Gorg's in our tank (you can see them both -->on this page of our site
). Both of these gorgonians are primarily photosyntetic, and have seemed to do best (for us) under MH
lighting. Both of these Gorgonians seem to have their polyps extended about 85%-90% of the time, and do appear to 'catch' a considerable amount of food when we feed the tank.
There are non-photosynthetic gorgonians, but these are typically difficult to keep, as it is extremely hard for an aquarist to provide the amount & type(s) of food they are used to getting in the wild. One exception to this seems to be the Yellow Gorgonian.
I have never personally kept a non-photosynthetic gorgonian, so I can't offer any personal insight on their care.