Went to bed at 2:00 AM this morning and my tank was great. Got up this morning at 8:00 AM and every fish in my tank except my GS Maroon Clown was dead. I've had this group of fish for about 6 months no problem. I ran to the fish store and got 5 gallons of their water and set up my QT
and got my clown in it.
Parameters (which matched up at the pet store):
All inverts are doing fine including my serpent star
Fish in the tank that died:
Yellow Eye Tang
The only external sign on the fish that looked out of the ordinary was my Naso Tang had black blotches all over it.
I added carbon to my sump. Any other ideas before I do a massive water change?