I have a pair and babies too
They like it hot. 85-90 on the hot side and it can fall to room temp on the cool side. they need lots of hides as they do not come out much except when its very quiet and dark.
**** make sure you are feeding the proper size of food!!!!! Mine are full grown and I feed them 1/4 crix. If your's are less than 6months old you'll need 1/8 crix. Make sure you dust with calcium and D3 every to every there feeding. I've also heard that they love tiny mealworms/waxworm.
Mine are 3"(female) and 2 1/2"(Male) full grown. I have pics in my galery.
Sand is ok but you still run the risk of impaction(as with any gecko)
If you have any specific questions PM me and I'll help out the best I can.
you can also search Viper gecko's on Google or Teratolepis Facitia(sp?) is their scientific name
Best of luck, they are very cool gekco's