People's blood is a water base with a high salt content. If someone suggested reducing the stress on people in maintaining that briny solution in their blood by misting them constantly with salty water they would be laughed out of the room.
True fresh water fish are adapted to fresh water. They thrive in it. True marine fish are adapted to ocean concentrations of salt in their water. Fish that come from brackish water will do best if you can imitate the level of salt they would experience in the wild.
Salt as a preventive - If you have a sore throat, you will often be told to gargle with salt water. For fish, if they have ich, salt can help.
If someone told you to gargle with salt water 5 times a day to prevent getting sore throats you would think they were crazy. Salt as an ich preventive or tonic strikes me as the same kind of thinking.
I'm done with my rant for now but the misinformation put out by people trying to sell salt gets under my skin and the constant salt water spray doesn't seem to help me.