I wouldn't trust salt to kill these things. Once upon a time, this same tank had brackish water....shoot, these snails have had quite a history...
I first got them in 2007. There were only 3 of them.
Started out with a freshwater tank. i more or less forgot about the snails. peek in on the tank one night, and sure enough, there were many snails.
Eventually, had to get rid of my fish... I washed the gravel in hot water, let it sit outside for a few days. gravel seemed dry (at least on top)...
set up the tank again, have a few fish in it. eventually i notice my snails are back! I don't mind them, as they only came out at night.
I end up realizing some of my fish are brackish fish. SO, I turn the tank into a brackish tank. It was brackish for a good year. snails still managed to survive.
decided it was silly to have a brackish tank with only a few fish that were actually brackish. got rid of the brackish fish, and switched it back to freshwater.
A few months ago, i got some marmimo moss balls. this was a mistake. after i dropped these in the tank, the population of snails exploded. they no longer hid underground. even after i got rid of the moss balls, their numbers just kept building.
Got some clown loaches, which just ignored the snails... got a team of about 50 assassin snails, which couldn't even dent the population.... tried trapping them in a bottle.... pulled out a good 1000 or so every morning, with no dent in population... tried starving them by individually hand feeding every single fish in the tank...
SO, this is a last ditch effort. I'm angry because i found a few tiny MTS in the new tank already. have no idea how they got in there. I removed them, and haven't found any more, but i fear there are more in there...