When I was diving in the keyes, I found brain corals at 100ft. I didn't go much lower, but I didn't see any evidence that they were deminishing in size or population density. I suspect they don't mind weak light, but they may not grow as fast as those at shallower depths.
Zoos also don't mind weak light. I have mine at the bottom of the tank, but they havent' been growing much. I just started feeding them twice a week, so we'll see.
