How much aquarium salt for 5-gallon drum?

I have heard that bettas like a bit of salt water aquarium. How much should I add my 5-gallon pail with a Betta? Are there benefits to add?

is a tbl spoon per 5 gallons, but if you have plants in the tank does not add salt will kill the plants added salt to freshwater tanks to promote healthy skin is not necessary unless brackish water fish and brackish water betta is not

Aqua Medic Percula 120, full HD,Reef tank, Corals, SPS, marine Aquarium, Salt water