Natural sunlight is your best source for UVB rays. As mentioned before, just be sure there is a shade retreat and never put them out in a glass tank! Probably be a good idea to have some water in the enclosure too. My vet recommended one of those big plasitc bins that you can get for storage. Not the clear ones. Just slide the lid back to create a shade area. You can get them at Home Depot and I think they cost less than $10. Watch for cats and dogs and Good luck!