I set up our first salt water acquarium March 17/07 and started 2 months ago with 3 pajama cardinals. Everyone is doing great. I added about a month ago a raccoon butterfly and noticed that it has developed a ball white spot on its back fin. It has had this now for about 3 and a half weeks but it has not spread and it seems to be doing fine. The cardinals haven't developed anything. The SG is around 14 so it is low and from what I've read these guys and supposed to be resistant to ick. What could it be? Please help.