Limpet snail?

[Tate]

My tank has been setup for 5 months and I just noticed it on the sand bed. It looks to have made a shell out of some live rock. The only live rock I've added was one pound 2 months after setup. The rest is dry rock. Is this a limpet snail? Good addition to have?

 

[Tate]

Pics would be helpful

 

[woody390]

Looks like a hermit crab to me may just be my eyesight though lol

 

[mr_X]

it's the shell of a whelk. I can't see if there's a crab in it or a whelk though. Meanwhile, some are ok and some are not. Easy enough to remove if it is a bad guy though. Just keep an eye on him as he grows.