This salt question has been a curiosity of mine for a long time. My API Aquarium salt says on it, "Freshwater fish actively maintain a natural balance of electrolytes in their body fluids. Electrolytes such as potassium, sodium, chloride, calcium, and magnesium are removed from the water by chloride cells located in their gills. These electrolytes are essential for the uptake of oxygen and the release of carbon dioxide and ammonia or ammonium across gill membranes. A lack of electrolytes may cause serious health problems for fish. Aquarium Salt, made from evaporated sea water, provides the essential electrolytes fish need to thrive in an aquarium helping them reach peak coloration and vitality. Aquarium salt improves gill function, reduces stress, facilitates osmoregulation and promotes disease recovery."
So that being said lol it recommends the normal 1 teaspoon for every 5 US gallons... the thing is I agree with most in that its a "freshwater" tank and needs no salt... but I place a small amount into my tanks in order cover every basis. I have read that my oscars and cichlids should have their water salinity checked twice a week... which is where the problem remains... having no hydrometer (uses water density to measure salt through a glass thermometer like device that floats high or low) or refractometer (uses light or something ie. you dip the lens in and look through a eye piece... more expensive) anyways i dont have one yet and am unsure that even if i could measure it what the point would be seeing how this question seems to have no 100% right answer!! soo... salt... maybe a little!