I agree. I am pretty sure the root cause to the fish loses was disease. I do have a quaratine tank now and will certainly use it. Yes my display tank looked ugly but that I am beginning to think would not kill fish. It looks like it was not chemistry issues at all. But the ICK was not easy to see. It did not help that I did not have a chance to see it in progress on the first two kills. But this last one, which I hope I might have saved, was classic.
I am beginning to think more issues in startups can be disease and less chemistry, but chemistry is easy to point too. You can measure it. You know what the targets are. So if it is off we tend to blame what we can see.
Disease is far less easy to pinpoint and symptoms are often vague. At least my experience is that it can be incredibly fast. Healthy to morbian in 4 days.