I have three pet hermit crabs, and they live in a 10 gallon fish tank. How often should I clean this hermit crab tank? How often should the sand be replaced?
Ideally you should spot clean daily (removing uneaten bits of food, etc.). Deep cleans (taking everything out, rinsing it off, replacing substrate, etc.) should be done about twice a year.
That being said, sometimes your crabs have different ideas. If one or more of them is down for a molt when you want to clean, I wouldn't worry about it too much. Just wait until they're all on the surface again, put them in an iso tank, and do your cleaning then. I've had to go a year+ between deep cleans before due to molting schedules and uncooperative crabs!