Does marine salt have expiration dates?

[rixmodi]

I have an old marine salt bag that has been sitting inside a bucket for the last two years approximately. It was opened and then re-sealed ("zip locked"). Will it still work? Have you had "weird" experiences working with old marine salt? I'm about to set a GSP tank. They are probably kept in freshwater, so i will have to add marine salt eventually. I just want to know if it's safe to use that old bag.

[Pufferpunk]

Only when it has turned into a salt block. Should be OK but the density may have changed.

[Troender]

You can use it, but you should measure the SG when using it. Old saltwater mix can give a lower SG than new ones. I experienced the difference once, when I opened a new one. Luckily I always control test the SG when changing water on my BW tanks.

[rixmodi]

Perfect... thanks