Hazel, you have to mix your own salt water using the same salt used in salt water fish tanks (one of the most popular one is Instant Ocean). Most people will mix about a gallon at a time and keep it in a sealed container.
Hermit Crabs ''grow'' by molting. They burry themselves in the sand during this process and can stay there for weeks. When they come out, they will eat a lot and bathe in salt water a lot too. I've never had a crab molt yet and I know I will be nervous because it takes quite a while and you always wonder if they're still alive.
I'm having a hard time finding shells for them though. If anyone can think of a place I could find some, let me know. They can't be painted or varnished...
Charlie, American Cocker Spaniel (06-26-2009)