Hi rainbowdarter,
This hermit crab is very, very common on the beach in Maldive .
I saw it myself when i'm there for 1 week honeymoon since 8~9 years ago.
They tend to come out from the sea to the beach about afternoon time and, not quantity of ten but hundred over. So I think it's not suitable in the marine tank bcos' it'll climb out of your tank everyday and crawl all the way out of the water to the land lei .
You got hard time to search for it every now and then, so it's good to release it into the sea !
Cheer