Zoanthis sociatus from Florida and the Caribbean needs very strong light, and a few from Fiji and other places out in Micronesa. They live in very shallow water that even gets dry and exposed to direct sun. But they will live in aquariums with just NO flourescents like PC or CF lit tanks. I have taken zoas that were way up under a ledge in the wild, and put them all over a tank lit by MH and VHO, under ledges, on the top of rocks near the top, halfway down the tank etc, and they did just as well. Same with zoas that were collected in very shallow water, even exposed to the sun, all over the tank and they all do well. Even in tanks with NO flourescent lights. Some that like a lot of light will stretch towards the light or the head will get wider, but they will eventualy get used to it and grow just as fast as the others. Some tanks will grow brighter zoas than others, it may be the lighting, water quality or some other thing. If they seem happier in the top, maybe move the rest to the top, or vice versa.