Duke,
That's true but sometimes you have at pick the lesser of two evils. That's coming from a fish farmer.
Try sending in sick fish to a lab to be diagnosed so you can use the "right" antibiotic. While your fish are dying the lab takes at least a week to get back to you (many times a more)and refuses to speculate or advise you on what to do in the meantime.
I've had at least one instance where antibiotics saved my butt. Romet is a broad spectrum antibiotic so if you're sure it's bacterial it can do the job.
That said most disease outbreaks are stress mediated so one should go all out to remove any stress factors such as low oxygen, overcrowding, less then optimum or more than optimum temps, bad feed etc. Many times if you think ahead and remove any stress factors ahead of time you won't have problems. However with fish farming at high densities that's not always possible.
