Here is what you should do on a daily, weekly, and monthly, basis!
Daily Remove any uneaten fresh foods from yesterday put fresh food in the food dish give the crabs fresh salt and freshwater mist the crabs wet the sponge
Weekly clean out old substrate wipe down the sides of the cage give the crabs a bath
Monthly Replace old sand sterilize hermit crab play and climbing toys clean entire cage
http://hermitcrabcare0.tripod.com