red claw crab requirements

[Koi Kameon]

Just purchased a half-inch red claw crab. Currently in 1.002 brackish water as store had it in full freshwater. I have seen the parameters for salt anywhere from 1.002-1.005. Anyone know which is best? Also, water depth suggestions from 3 or 4 inches up to 8 inches. Any ideas? Already have wood, sand substrate, java fern for it, and plenty of dry land. Putting java moss in soon. Maybe a few male guppies for company.