Just lost ALL of my fish (well most of them), only a few left, cause unknown, it was brutal, within seconds dropping like flies. Right after a water change too, can't figure out what went wrong. The water parameters were near perfect, I think maybe some suntan lotion may have been on my arm from before even though I washed it good prior to sticking it in. This has never happen to me, it was a routine water change. May have to break everthing down and clean everything really good. Bye Bye beneficial bacteria.