Lost my coral beauty this morning in quarantine at Day 5: QT was precautionary (new purchases) and not for treatment of any specific disease. When I checked on the QT at 0800 this morning, the angel was swimming at the surface...and then, lazily, upside down. At 0830, it was stuck to the powerhead, with very rapid breathing. I gave it a FW dip (nothing visible dropped off) and placed it in a jar for observation. At 0900, it was gone. No obvious signs of disease (although I didn't see it eat yesterday) or trauma except the rapid breathing (and swimming issues), and colours were bright and vibrant. Ammonia is "safe" on the seachem badge, and copper was being ramped up slowwly (currently at 1.02) because of a Lubbock's fairy wrasse. SG is 1.024. I've never had a fish go down this quickly.
And yes, the other members of the QT are okay (so far): the fairy wrasse and a lawnmower blenny. QT is a 15g, and equipped with a HOB filter, heater and a MP10. I through in some filter media a few days ago to help with the nitrifcation process, and put some turf algae in for the blenny (which it hasn't touched, of course).