It is important to emphasize that salt should not be used on a daily basis as a preventive measure or health booster. - Just as a healthy person is not recommended to take antibiotics daily to minimize the risk of infection.
In fish as well as in humans, superbugs can develop and become resistant to antibiotics, thus reducing the effects of treatment. So, if you constantly add salt to your fish tank, there is a high chance of developing diseases that will be able to cross the protective "salt barrier". This will eventually result in the need to add increasing salt concentrations.
Remember, it is a freshwater aquarium and it doesn't require large amounts of salt in the water. Therefore, use salt sparingly and only when necessary.