Demise of a yellow tang - what's the cause?

[loonz]

Hi,
Have been most unfortunate to lose a precious pet this morning that has been with me for the past 2 years(at least).Here's how it happened:
I wanted to combine my 2 tanks into one so i removed everything from tank A(including yellow tang) and rearrange the rockwork with rocks from tank B together with tank A's. After 2 days i put all the livestock back into tank A and everything seems fine for a while.I did a 10% water change.
Yellow tang has always been a voracious eater but last night it looked emaciated and did not eat.It had vague red/orange patches on its body.This morning Yellow tang could not be found!It's a 2.5" fish in a 65g.I fear YT must have become breakfast for the large CBS in the tank.What kind of disease is this?Anyone has any idea and has it happen to anyone of you out there?Maybe some of you might think otherwise,but now my Sailfin has lost his playmate of 2 years.

P/S: i fed the tank frozen red plankton from MBF Fishfood(Belgium)for the first time the day before it looked ill.

 

[danmhippo]

The coloration indicated a clear sign of stress. Did you have a hard time trying to net the Y-tang? Could it be the stress endured during the netting? Could it be that the spine is injured during the netting as well? How is the water condition right now, I assume there must be a lot of detritus stirred up from the rock rearrangement. How is the nitrite?

BTW, a tang with you for at least 2 years, I would assume the size must be at least 5", not what you indicated 2.5".......that is a rather small yellow tang!