I have been a big fan of tangs over the past 20 years. I have about 10 tangs in my 180 gal
reef currently and it will soon be 1/2 that. The problem I have is most of them are getting thinner. The easiest sign a tang is healthy is thickness in the head along with the full belly. My tangs seem to be eating a lot but after about 6 months, you can notice them to start to get thinner behind the eyes. So much so that in my buck tooth tang, you can start to see his spines. It seems the only two it has not affected are the two small hippos, the yellow tang and the Sailfin. The rest are eating everything but continue to get thinner. The last time I encountered this issue, I was told it was a disease that affects surgeon fish and I don't remember how I treated it.
Looking for some assistance and any help would be appreciated.