Getting your crabs
Before you buy a crab, get its crabitat ready to be used. You will need a substrate, like forest bedding or Eco earth. DO NOT buy colored sand for your crabs. For the tank, hermit crabs need at least ten gallons, so that Kritter Keeper that the Petsmart lady said would be perfectly fine, is not perfectly fine at all. Don't get a wire cage. Just Don't.
Also, don;t buy just one crab. Buy two or three. Hermit crabs are very social with other crabs, so make sure you have some buddies for your crab.
Buy some good food for your crab. Petsmart and Petco have good options. Variety bites are good, but also get them a treat. Every fifth time you fill up the food bowl, fill it with your treat.
You'll need two water bowls: one for fresh water, and one for saltwater. Buy some soaking salt (Make sure it is the brand All Living Things, other brands are poisonous to crabs) and follow the directions on the salt to make your crabs some nice soaking water. For the fresh water, buy dechlorinator (Also, buy it from All Living Things) and put a drop into your freshwater bowl.
You also need to get something for them to climb on. Get sticks from your yard, boil them in water, and set them up around the tank. Also, get a wire climbing net. The crabs will love it.
One thing you absolutely NEED is extra shells. DO NOT get painted shells. They will kill your crabs.
Get a humidity gauge and a thermometer. Crabs need 75-85 degrees (F) and above 70% humidity. Get a heater with a timer, Zoo Med's heater with a clock timer works fine. Set the timer to be on for 1/2 an hour, then off for an hour. only use this if your house is under 68 degrees. For humidity, put a wet rage over the lid of the cage, and spray the tank twice daily. Avoid or take out the food during spraying. Get two sponges, wet them daily, and place them on each end of the tank.
Now you're ready to buy your crabs! get 2-4 if you have a 10-gallon tank, or, if you have around 30 gallons, you can get up to 10 crabs. DON'T get crabs with painted shells. You are supporting a very cruel pet market if you do. Crabs' shells are broken, smashed, and crabs are forced into scratchy painted shells with no other options. Make sure you have natural shells.
You're now an owner of some of the coolest pets ever!