Snails at Lucky 97 Market

[Myanth]

Hey all, I was in Lucky 97 Market yesterday to get some Nori and found that they had a whole bunch of live snails. They have a grey shell and black foot. I am pretty sure they were in salt water as it looked like the overflow from the crab tanks was feeding their tank. Just wondering if anyone knows what they are and if they're good/bad indifferent. Was thinking of getting a few for my sump and see what they do. I have seen similar looking snails in tanks but usually FOWLR tanks. I have a few hermits in shells that look identical.

Figured I would ask.

Mike

P.S. great place for nori, frozen gobies, minnows, etc.