Can i use loner crab items on fiddler and red crabs?

I just get a fiddler and red crab for christmas. Ive been looking up things and found they obligation to be in brackish wet... so, can this be used in the container? :

And can this be used in the container as well? If I used the brackish would i still need something resembling this?

Also.. What kind of location and stuff do i need to put within the tank. Please relieve me as this is the first time owning crabs and i want the, to be happy and natural! :)
Answers: No. Those salts are for making a bowl for the crab to soak surrounded by. Your crabs should have a reservoir with give or take a few 70% sand and 30 % open wet. The water should be "brackish" which scheme about 1/2 the salinity of brackish water. Buy oceanic salts for making a saline water container and follow the directions for brackish water.

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