dbosman, thanks for elaborating on your original post, much appreciated. :thm:
I've got one more question for you & then I'll let you be. In your opinion why is salt over recommended for tropical fish? I'm not questioning your opinion, I just want to fully understand why you are of this opinion to begin with. Thanks.
The problem is freshwater fish evolved to live in freshwater. Body chemistry such as ion exchange require fresh water. Putting freshwater fish to salt solutions upsets the body chemistry. Will they survive? Perhaps, but generally at the cost of health and longevity.
The cure for syphilis used to be injected mercury or arsenic. The dose for a cure is just slightly less than a lethal dose, and mistakes were made, but the alternative was a lingering deteriorating life until the patient died from brain damage. Did it "cure" syphilis? Well, yes.
In the early days of fish keeping, and very specifically prior to 1944, there were no antibiotics commercially available. The first production antibiotics went to war. In 1944 they became available to the public. The antibiotics were one. Penicillin.
What fish keepers, and any medical practitioners, had were serums, salts, acids, heavy metals, sulphur compounds, dyes and other chemicals that were made into cures, tonics, and "medicines". Some of them worked. Sort of. Bleeding still works for some very specific medical conditions. That doesn't mean it's recommended for influenza.
Salts, and there are many salts, were used to treat fish because there weren't better options. A hyper-saline solution will kill or seem to kill many parasites and bacterial infections. Why? Some parasites essentially explode or implode. The working process is ion changes shut down the life of the parasite. Hopefully before the ion changes shut down the life of the fish. It was worth the risk as the alternative was to lose fish, but... It was the change in salinity that killed the infestation. The fish were always restored to their freshwater tanks after the treatment.
Unfortunately there are pet shops, Petco for one, that still recommend keeping salt in a freshwater tank. It's a great way to sell medications.
Keeping salt in a freshwater tank actually increases susceptibility to disease as the fish are always under stress.
More unfortunately, far too many pet books, web sites, and even forums, pass on lore not research.
There are still people who believe Xxxxxx can cure any number of things, despite reams of documented research proving otherwise because so and so said it worked.