We took the school hermit crab over winter break and it was a pain in the backside. We had to monitor its temperature all the time, and there were two different chemical treatments for the water, and its food pellets had to be soaked until they were exactly the right consistency. It had to be moistened multiple times a day and it was stressed about having its terrarium relocated to our house so it wouldn't eat.
Lesson learned: hermit crabs and humans have incompatible native environments.
