Oh dam..sorry to see that. No open windows where any kind of chemical could have gotten in or visitors or anyone that could have put something in ur tank?
Back in 07, some roomates at the time thought it would be fun or funny to get drunk and spray something in my tank while i was at work ....and that wiped out all my fish kinda like velvet.
Oh my. This is heart breaking. I have been trying to make sure I don’t put my hands in my tank for anything. If I do, I make sure I’m washing and sterilizing with hot water before I do because of all the hand sanitizer. Sorry for your loss.
Sorry for your loss. I went thru the same thing- lost two clowns, an anthias, a royal grama, a mandarin, and a molly. Tank had no new additions for months, and no changes. Just one day clown was dead- rest of the fish looked ok. Next day the rest of the fish were dead.
One molly and a algae blenny seemed to not be affected and are actually still in the tank- I never added any more fish to that tank as I never went fallow so I assume it’s still in the tank.
I have a few tanks, and when I get around to it I’ll put those two fish in QT and let the tank go fallow.