Total wipeout- ALMOST

[MartyG]

I have been doing fish-only salt water aquariums for 25 years, but just had a first disaster. The dead fish don't seem to have died from ich. There were no white spots. Some of the fish exhibited ragged and red fins. I have not had time to test the water yet, sorry.

I have lost all but one fish (a lunare wrasse) in my 90 gallon tank. I lost an Emperor Angel, 3 tangs, a Picasso trigger and Cuban Hogfish. these fish just keeled over within 24 hours and died. I have had this tank running pefectly for 6 years in this location and 3 years in my former location. My fish have grown and thrived.

Whatever the cause, ( I have a few theories, including bacterial infection) what irks me is that this lunare Wrasse is doing just fine.

Here are the questions, never having dealt with this before:

Do I let the tank run the way it is for a while, doing nothing?
Do I do massive water changes?
Do I break down the whole thing and scrub it clean and start from scratch?

advice appreciated

- Gilman