I did 10 days in trifecta and no lights kept fish in the dark. Don’t worry about it eating. It’s too sick to eat now. About three says after the antibiotics then try feeding. It’s in septic shock with the fin loss and bone showing, so it won’t eat. Just follow the trifecta and pray. So sorry for your tang.It’s never been with another fish. It went straight into quarantine, but I agree, that’s what it looks looks like. Now it’s fins are completely gone. You bones are sticking out of the top of the dorsal fin so whatever it is, it’s taken the flesh off all the way down. What should I try about the eating? It’s not going to last much longer not eating.