Anyone successful keeping Christmas Tree Rock?

[Chin_Lee]

Does anybody have good success in keeping the Christmas Tree rock alive? I have had one for about a year and its been doing well for the most part but it has recently started to recede and I'm not sure why. I've looked carefully and closely at the porites polyps and have not seen any of the porites flatworms. My rock will encrust and then recede cycle so i'm not sure what i'm doing right or wrong. any advice would be great. thanks
cwlee