Xenia can be mysterious. Some people cannot keep them alive no matter how hard they try, some people can't kill them fast enough to keep them from taking over their tank.
Some helpful findings:
1. Acclimate well, Xenia are very poor shippers. That extra 30-45 minutes may be annoying, but it could save you the money you spent on the coral and the grief of watching another one fade away.
2. Keep your pH up, I have found that Xenia show more extension and activity in an aquarium with a higher pH. In fact, I have used Xenia as a natural "test" for pH and found that when the coral began to shrivel, a quick test found a drop in pH.
3. Keep your specific gravity/salinity up, the same results found with pH are also found with higher sg, ex: ( 1.023-1.026).
4. Trace elements. I had heard the old argument about Xenia and trace, specifically iodide. I always thought it was another one of those myths spread around by "the fish guy" or any other random hobbyist. But, out of boredom one day I shot some trace directly on a retracted Xenia which displayed an immediate response in extension and pulsing. I can't prove anything scientifically, but my eyes know what they saw.
Good luck, Joseph :thumbsup: