Mine are happy as a lark and just keep breeding with no salt at all in the tank. I completely disagree with that stickied thread but I am not a big time author of fish articles so the stickies will stay as they are. Many, but obviously not all, fish that are called mollies will die if put into a brackish situation. Some of the ones that tolerate salt quite well are the most commonly seen ones in the fish trade. Because the fish need a high pH and high mineral content, the ones that can tolerate salt will do better in a sea salt solution than they will in a soft water tank. It has led many to believe that they require brackish water. Nothing could be further from the truth and nothing will convince those who believe they need salt. I gave up on trying to convince them long ago. I just go on breeding nice fish in very fresh water.