If you are new to hermits I will let you in on a common practice amoung them, they will kill each other for shells.
Provide them with extra shells. I try to keep 2 extra shells in the water for each hermit. They will molt and exchange up to the next size and so forth.
Otherwize when one molts it will become a target from another to get its shell.
When I collected my last batch of hermits, Gulf of Mexico standard brown banded common sand scuttler variety, I introduced (completely sterilized) pretty shells that I have collected through the years from around the world (Belize, Cuba, US & B Virgins, Hawaii, Johnston Atoll, etc.) at the same time.
Every single hermit, 30-35, exchanged shells within 15mins. And then proceeded to exchange again in a consistant pattern of house hunting, for about a week.
I left the old shells to become fodder and micro havens for pods.
Funny, they prefer my cleaned collected shells over their shells they brought with them from the Gulf.
Anyway, add more shells, with some size variation. Just because they are hermies don't think that they are immune to stress. Give the little guys some choices and they will live longer healthier lives.
Ray Boemler
www.peanutbutterjellyfish.com