This is terrible and i am racked with guilt, as I should be. I have a 40 gallon aquarium with 2 corydoras, 1 skirted tetra, lots of plants, and until yesterday 1 large angel fish. 2 weeks ago I foolishly introduced 2 skirted tetras and both were dead within 48 hours. 4 days ago i noticed ich on the remaining tetra, so began treating with melafix in the food and changing a couple gallons of water each day. All seemed ok. Night before last,at bedtime, i noticed the angelfish, who was at least 8, swimming with its mouth almost straight up. I changed a gallon of water and went to bed. In the morning the angel fish was mouth down against the air stone. It normally moves its eyes around at least. I saw zero movement. I netted it. Nothing. I looked for eye movement, gill movement... nothing at all for several minutes. Mouth stayed shut. I decided it was dead and buried it. Now i cant stop thinking i killed it when i removed it from the tank. I can't undo my actions but for future reference, could that poor thing still have been alive but had absolutely no movement?