Hi Tin,
I grow xenia in my tank all the time. I have no idea why it likes my tank but here is a few things that I have noticied over the past year.
1) Water consistancy. I do water changes with the same salt every 3 weeks and it matches my current params.
Alk 8, PH 8.0, SG 1.025, Trates run between 2-5, trites 0, ammonia 0, phos 0, CA 400. Idodine I add one drop when things are not opening up as much as they usually do.
Some of the things I have noticed: If the Calcium is below 400 or abve 450 they do not like it. I check each week to make sure I am in the zone, they do not mind if the trates get up high 7-10 but do not like when they are above 10. Temp is steady 80-81. They do not seem to like below 78 or about 82. I do not add any extra trace minerals. They are in the salt. iodine is the only exception. They use quite a bit. I keep them high up in the tank. They love the MH. I add 2 caps of DT's every 3 days. They seem to like it and grow quite fast.
If you have any other questions just ask, I will try to help.
Sorry to hear about your xenia.