green acro?

[sumpfinfishe]

Looks like RTN to me, did you have any major swings in the tank or in the bag on the way home from the store. SPS are rated a harder to keep coral not only because of there lighting and Calcium demands, but also because they do not tolerate shifts in water parameters too well. A Temp., Sal., PH, Ca, or Alk swing could have caused this coral to die, not to mention a change in lighting or water flow could have too.