Aquarium Salt and Betta

[Sizzlingtree]

We are planning to house a female betta with some guppies and black mollies. Since the latter two need some aquarium salt (lightly salted according to the label) is it alright for the betta to get some? Will it harm or affect the betta negatively to be exposed to aquarium salt? I know that aquarium salt is kind of a cure all and I added some to a 15 gallon tank that we are prepping for the arrival of our fish. The female betta is already in there. Is this alright?

Any help would be appreciated.