Some people say no because it could effect their labyrinth organ but i say yes. When my gouramis had ick i had no choice but to put salt in the tank and they were not effected at all if anything they became more active than before they got ick. They have been in a tank with salt now for a long time with no problem so its really up to you..
A bit of salt is fine, just don't use it unless you know how much will work and there is a good reason for it. For 98% of the time there is no need for it, and for the other 2% it's optional.
