I must say, I just cannot figure these guys out. I have one that sat on the bottom in the sandbed for months and did great in moderate lighting and current, even surviving a tank move and a water quality emergency mishap that has now been corrected.
Strangely enough, now that all my other corals are doing great, this darned thing has closed up and I just don't know what to do with it! When it was doing well, it opened up very nicely and when the feeding tentacles came out, I would be able to feed it small bits of shrimp, which it happily ate. Now, I'm just not sure what to make of it! They are reputed to be hardy corals, yet I've heard of random things affecing other ones as well...my first one, for example, died from overpecking from a tang.
I am hoping that now with my tang-free tank, I will have better luck, because I also have a metallic red brain that has opened up very nicely, but the green one does not seem to be very happy. Do leave room between any of these brain corals and other corals if you are to keep them together, as it is a stinging and competitive coral.