IME xenia is very hard to say it will thrive on certain conditions. I bought one small frag almost 5 months ago and now I am trading it @ LFS for other corals. I have it under high flow, high light, low flow, low light and even in caves (no lights). Usually the one right under MH on top shrinks when MH goes off (slight PH drop) and back to normal within 15 min. Here is a pic where it is on high light with high flow.