Hi Fishiee
AM tanjong katong have some blue legged hermit crabs and some normal brown colour hermit crabs, an advice if you want to keep hermitcrab, get/buy some slightly bigger empty shells, once hermitcrab outgrow their existing shell, they need to change shell.
Hermitcrab do not live forever, lifespan is between 2-3years. Like all crabs and shrimp, they need vitamins for them to molt properly, for me, i add iodine and calcium.