Be careful of what you ask. Xenia can overtake a 29g tank real fast. No xenia food is needed. NOT NEEDED! They feed from the light and the water cloumn.
Also, I'd consider placing that rock up high with the xenia on it. If you place it low, it will creep upwards fast and cover a lot more real eatste than you ultimately want, believe me.
All xenia is "pulsating" yet there are different varieties. Some gro faster than others. Elongata is the most popular and grows too fast IMO
. Will take over other corals in it's path. Pom pom is another. More silvery looking and slower growing.
I'd stick with what you've got and go from there w/out adding more if it were me. Also, I don't believe it ships very well at all.