Red Claw Crabbie not eating

[b.greene]

About 2-3 weeks ago my son used his savings to purchase 2 small red claw crabs and a 10 gallon tank (half water, half land). After a few days we found a molted shell. I left it in the tank because I had read that they need the calcium it provides.
Here's the problem. The crabs do not seem to eat ANYTHING! The sinking shrimp pellets just sit there until they get fuzzy. I tried a green bean and the same thing happened - and it stunk!
A few days ago I found a dead crab. I left it 2 days and then removed it (I wanted to make sure it was actually dead).
We thought the crabs would be so fun but all they do is hide under the filter.
Any help?

[mellowvision]

they may not eat during moulting periods... but I wonder about other factors... salinity, temperature, amonia levels...

[jm1212]

are you using marine salt to make a brackish setup?

[b.greene]

Yep, I some marine salt when I set the tank up.

[Bobnova]

Did you cycle the tank/filter(there is a filter, right?) before putting the crabs in?
Are you doing water changes(with marine salt to the proper specific gravity)?

Crabs aren't especially low bioload types, in 5g of water in an uncycled two of them can(and will) run into ammonia/nitrite issues fairly quickly.