Rocks may be added. They also need to have extra empty shells in the tank so they can change shells when they grow larger. Land hermit crabs can not reproduce in captivity. Their eggs must hatch in the sea. Like other crabs they must shed their outer ex-skeleton.
Older crabs molt less frequently but require the same care.
It is known that some crabs have been kept in the home as pets for as long as 15 years. The hermit crabs like to live with more them one, you should get at least 2 or 3 or 4 or maybe more. They will have a better activity schedule. You will have a much more enjoyable time watching them.