I have in my SW
tank an Atlantic Blue Tang. I got him in February and he spent 6 weeks or so in a quarantine tank before he went into the main tank. Neither he, nor the other tang in that QT showed any signs of ich or any other disease during that time (or since then, up until now).
In early April, they were moved to the main tank. There has been a little aggression during this process but no signs of disease. This weekend I saw the Atlantic Blue Tang flashing -- I saw him do it twice. After the first time I watched him very closely for a half hour and saw him do it one other time. I haven't seen it since.
From what I know about ich, there's no way that there's ich in that tank. Since the tangs were added in April, the only thing I've done to that tank was water changes, with one exception: I added about 10 Nassarius snails a couple of weeks ago. I didn't think that snails could carry ich.
It's been a couple of days since I first saw the flashing and I haven't seen any other signs of anything bad, including the flashing. Is it possible that there's a disease in my tank right now? Or did this tang just have an itch or something? Maybe he was just messing with me?