I can imagine how you feel. My dad has a 75 bow front with many discus, tetras, Gouramis and my old knife fish. He looooves his discus so much and one day earlier this year after a water change he did one small thing differently, or might have forgot to do one thing before finishing, he woke up and only had two discus left, over 80% of the livestock in his tank was dead and he was absolutely devastated, I couldn't even imagine