I have a 96W PC on a 16g nano-reef, and my xenia (placed in the center of the tank, about mid-column) grows like the weed that it is! It grew higher in the tank as the PC bulb aged. When I replaced the PC bulb, the Xenia colonies shrank back, as would be expected.
Xenia seem to also like good water flow. I have about 160 gph flow directly on a colony and it doesn't pulse and bloom like the other colonies that are not inline with that flow. When I shutdown my pumps, the xenia go flacid.