Saying salt is unnecessary for fish that naturally occur in waters with salts is poor advise. Fish that occur naturally in waters with salts evolved their methods of hormone production and osmotic regulation in those waters. The permeability of egg membranes also depend on the elements contained in the waters the species evolved in. While a species may do well in waters without their natural components, it must be considered that the species would fare better in waters that most closely match what it evolved in.
Replacing lost salts from water changes is as easy as using a hydrometer. And, the 'buildup' of salts from evaporation is on a par with the drop in lake water levels between rainy seasons. So, no problem unless the aquarium is allowed to nearly dry up.
I've used epsom salt to treat bloat before metronidazole became available OTC. But, I wouldn't use it as the 1st addition of the prevention of wound infection. The system won't benefit any better with the addition of magnesium and sulfur in epsom salt than with the calcium chloride these fish evolved in.