I added a small frag of xenia over a year ago....
Needless to say, I have had no problems with it growing, spreading, fragging,
and just plain pulling off my rocks when I get tired of it.
I do use a carbon bag in my sump, which I think most do these days, it can
help pull out many toxins that corals use as defense in your tank.
The coolest thing about xenia, is it will move to a place it likes over a period
of time.
Mine stays at the top of the tank, gets lots of water flow and light and even doesn't mind a nip from my Atlantic blue tang now and then.
Temp. hasn't been a problem for me at all, it gets hot here, and I haven't had any problems, even when the tank is 84, fortunately that is as high as it ever gets.
It is one of my favorite corals, and I wouldn't be without it. It is easy to keep, frag and always seems to pulse faster with a good dose of phytoplankton.
Good luck