Natural Environment of Ghost Shrimp?

Hi.  I wonder if anyone out there has any solid information about the
natural environment of these ghost shrimp?  I've had some experience keeping
them, and have myself noticed that they are rather short lived.  In each
case of death I've noticed that the shrimp I had tended to turn from
transparent to a milky white before they died a day or two later.  I've
always wondered if some environmental factor was at work.  Could it be that
these shrimp are more accustomed to brackish waters or cooler temperatures?
Maybe the pH or hardness of the water was off for them?  Is the color change
a stress reaction?  I think knowing a little bit about the natural
environment of these shrimp might provide some answers.
        -Jerry B.