Thanks for the ideas Yote and LF. I'm honestly not sure its lymphocystis (though would be glad if it was since its mostly non-fatal). It doesn't really look like a tissue sac. The fin is torn and looks like its rotting away, the edges where there is fraying are turning white and hanging off. The fish has come out a few times today but not long enough for me to get a good look (or picture). I think it hasn't really figured out that I am the source of food yet and is very skeptical of my presence. From what I did see though it looks like more of the fin is gone so whatever is going on is progressing. I don't think there is any chance of catching it. Its just weird - this fish came from Divers Den where it was qt'd and conditioned, and obviously appeared and acted healthy enough for them to sell it, and it was eating well when it left their facility, so its hard for me to believe that it was sick when it arrived. None of my other fish have ever shown any sort of fin rot or viral issues (except for 2 of the 3 chromis I added when I started the tank, they developed weird black growths that we wondered if they were viral or fungal). This white symptom is not something I've seen on any of my fish in the past, and everyone else is acting and looking totally normally. I guess I'll just have to hope that (1) it goes away on its own or (2) if it doesn't and the fish dies, that it does so out in the open where I can retrieve the body. A 5" decaying fish isn't going to do my tank any favors LOL
North, their colors are absolutely stunning. I saw one in an LFS several months back and knew I had to have one at some point! Mine is showing more blue than purple right now, but I think that is probably stress related and it will look more purple when it settles in - even now though its an absolutely gorgeous irridescent periwinkle! I have screens covering everything and think I will buy some weak magnetic strips to really secure the screens down. I've been doing a lot of reading on them and read that some will torpedo out of the water and actually hit the ceiling! I plan on keeping mine securely in the tank :) Good to know that they are really good hiders and take more time than most fish to settle in. I'll take it as a good sign that he's coming out as much as he is then!