Every now and then if my regal tang gets stressed, he gets an "ich" cold, when everything calms down he gets "well". He is a great water quality indicator. My yellow tang gets teeny black spots now and again in times of stress, but they also get better. I've had the blue tang about 3 1/2 years and the yellow about 5 years. I have another brown tang who has been in my tank for 5 years and in the guys I got him from for another year, so I know he is at least 6- 7 years old. (Watch him die tomorrow.) I don't really panic about "ich" the way I used to. Although, I do try to "fix" whatever the problem is that is stressing them. I am a tang addict and have 2 more in that same tank.