I have had the same experence with xenia, I added a small frag a over year ago, it spread to a good size, about 6 in sq. Then one day it just all started to died off, and was gone if a few days. Didnt notice any other changes, water was OK. I have tried to add another small frag since then with no success. I would like to add some back, I do miss all the pulsing hands.
Has anyone ever figured out the right conditions for xenia? I know some have success, and other with great tanks cant keep it.