Sorry to hear. I feel your loss.
We lost our most favorite fish recently due to my failure to detect a disease.
I put some fish through QT but missed it. Put the fish in our DT and the main guys started dropping like flies.
It was heart-breaking to watch our buddy do the herky-jerky death gasping thing. Then the total still-ness after. All the time I'm telling him to 'breathe dude, breathe"
Something I'll never be able to forget
I'm not generally over emotional, but it's given me some nightmares about tank leaks and such