ok ,,this might seem like a silly question but here goes

ive seen hermit crabs sold at fairs in the tiny tank , with no water in them ,,are these the same as salt water hermit crabs ?

No, they're not.

If you want salt water hermit crabs then buy Red Legged Hermit Crabs, or Blue Legged Hermit crabs, which are fully aquatic. The ones not in water are not supposed to be in water.

No they are not the same, those cute little guys will not live in a salt water tank. You would need your own little container for them, a sponge thats always wet, and some hermit crab food. Also...don't be a jerk and paint their shell. They don't like that. It will throw off their balance.

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yeah not the same i got a link for a site about hermit crabs and those crabs you saw wernt even in a proper tank HCA: Hermit Crab Association® :: Index check it out its really great

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The Two Banded Clownfish, originates from the reefs of the Red Sea. It has a reddish-brown and orange base color with two white stripes and an orange tail. The Two Banded Clownfish is one of the liveliest of the clowns that brings both activity and character to any saltwater aquarium. mates. 20 Gallon
In an aquarium, it will readily accept most meaty foods and herbivore preparations.
Excellent Reef Fish
Easy Level of Care
3/4" to 1" 1" to 1-3/4"

sponges arent really great and neither is hermit crab food commercial food in stores is got preservites that are bad for the crab and sponges keep filth in so you want them drinking their own filth? and its not a tiny container the most is a 10 gallon and dishes of fresh and salt water

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The Two Banded Clownfish, originates from the reefs of the Red Sea. It has a reddish-brown and orange base color with two white stripes and an orange tail. The Two Banded Clownfish is one of the liveliest of the clowns that brings both activity and character to any saltwater aquarium. mates. 20 Gallon
In an aquarium, it will readily accept most meaty foods and herbivore preparations.
Excellent Reef Fish
Easy Level of Care
3/4" to 1" 1" to 1-3/4"