My pulsing xenia's are spreading quite well. While I haven't had any problems, others have had trouble keeping them under ideal conditions. Sometimes they will stop pulsing when introduced to a new tank, also. Entire colonies of xenia have been known to crash, even after flourishing for several years under the same conditions.
Some reefkeepers advise using iodine for xenias. In my experience, when I was adding iodine for my mushrooms some of the xenias closed their polyps and stopped pulsing for a while.
JMFFEO
(just my far from expert opinion)