It will take quite a bit...can't remember how big your tank is without going back to page 1 though, and I'm too lazy (tired) to do that right now.
You aren't pouring the undissolved salt right into the tank are you? The best way to do it is to siphon out some tank water, add salt to that, and pour it back in. Or, do a 10-25% waterchange and mix the new sw to a higher sg.