van787,
I just brought my xenias home last weekend but can already agree with what the other people have told you. I initially placed the xenia under a ph that was about half way up my 45. They didn't seem to like that......stayed closed for much of the day. I moved the ph up to almost the top of the tank and they, so far, look great! My lighting is 175w 10K MH and 2 95w VHO actinics. I have the xenia at the bottom of the tank.
Jim