Thankfully, I am not having any problems with my fish or my tank, but I've always wondered where these various problems come from. If not from introducing a new, sick fish or not bringing stuff in on a new plant, how do these various problems and diseases start? I mean, are some simply endemic to fish and will appear when a fish is under stress? Just really curious about this. In addition, I read that to rid a tank of ich one should raise the temperature to 84F and keep it there for two weeks. Another person said ich dies at 89.5F. I hope I do not need any advice on this, but if I ever do, I'd like to know what to do and quick! (Again, where would it come from?) Wouldn't such high temps harm other fish such as DGs, Neon Tetras or Corycats? Thank you for any and all comments.