Best salt to clean belly piercing?

The best salt is the salt you don't use. You don't need salt to clean a piercing, never have never will. Yeah there will be some who say "my piercer said", yeah what ever, bottom line cleaning daily with diluted liquid antibacterial soap and a water rinse and leave it alone. Unless you know exactly how to use and make a saline solution, don't bother, you can mix it too strong and end up burning the tissue with the concentrated salt.