My 75 is about 4 months old now and the only coral I have is a single frag from a zoanthid (it was cheap and supposedly easy to keep). It's doing great for a while and has even added 2 new polyps. About 4 days ago some of the heads started doing this weird half open/half closed thing (as in the pic below). The frag was dipped in Coral RX when I got it and seemed fine.