Because they can.
U CANT TOUCH YOUR CRAB OR IT WILL LOST IT LEG OR CLAW...put rock in it for the fiddler crab to sit on...u have to have salt water or your crab will die...
You can get a fiddler crab at most pet stores. I got my fiddler crab at Walmart because they were cheap. However you can also go to Petsmart I know they have them and I am sure Petco will have them too. A lot of the petstores have fiddler crabs.
1-5 gallen shuld fit them nicely just make sure part of the tank is land
To take care of a fiddler crab, provide a tank with brackish water (a mix of freshwater and saltwater), a substrate for burrowing, and places for climbing. Feed them a varied diet of fish flakes, algae pellets, and fresh vegetables. Keep the tank clean by performing regular water changes and monitoring water quality.
Fiddler crabs are from the mangroves so they are not suited to life in an aquarium. Maybe a small swimmer crab could be kept in a marine aquarium provided you know exactly what you are doing and have all the necessary equipment.
A tank
Hermit crabs love a large area with lots of space to play in and plenty to climb on an old aquariam tank is perfect for hermit crab/s
1000
You can keep a horseshoe crab in a saltwater tank, as long as you have a large sandy bottom. If the horseshoe crab becomes too large, or starts knocking things over in the tank, get release it back into the ocean or get a bigger tank.
-( 0 0 )- -| |- -(____)- <<<<< this is an example of your crab!
You should clean your hermit crab tank once a week to maintain a healthy environment for your pets.
Fiddler crabs come from the mangroves where there may be a regular fresh water flush so they may survive for a short while in fresh water. They will not however be able to live for long because they need the calcium and other elements in sea water in order for them to get the neccessities for shell growth.