I'm confused. You mentioned that you were given a conch shell from a net. But then you also have this hermit that is in a shell w/barnacles. I see two shells in the tank. I also see the hermit. But, is the conch also alive? Did the hermit inhabit the conch shell that came from the net? But, then moved into this other shell. Just trying to get the story straight.
The cycling of the tank can kill both these critters, that is one reason why many are recommending taking them back to the ocean. And I agree w/ others that the conch is very hard to keep fed, it can slowly starve to death. Conches are for the more experienced to have. Hermits are easier to keep. And yes, they can stay out of water for long periods of time as long as their gills stay wet. If the gills dry out, they die. This is how the hermit survived.
If the beach is four hours away, perhaps you can find a pet store that keeps salt tanks closer then the four hour drive and see if they can take the critters. Otherwise, they may die while in your care.
You will have a lot of reading to keep a salt tank, you need to get a hold of a book that provides the basics. There is too much to convey online. Plus, online you may get little bits of info and not the whole picture on how to keep salt tanks.
Good luck and keep us posted.