These little Crabs naturally occur in Northern Australia. Living in Rivers and Billabongs. During the dry seasons (Normally in winter) they will borrow down into the Sand/Mud until the summer rains come again.
They are a Northern Australian Species so they prefer warmer tempratures (18C-28C)
PH 6.5-7.5 (But keep it over 7 they don't like acid water)
You can keep these Crabs with other fish. But faster swimming fish would be better, as they will try and eat a fish if they could catch them. If he finds a fish that is sick, dead or dieing it's going to be food.
It is also recommended as they are Amphibious by nature if you can have a rock or driftwood protuding out of the water providing a little island to sit on they will appreciate it.
They are a fascinating creature and are great fun to watch.