You can get it from outside as long as no pesticides have been used where you are digging for the dirt. I get mine from the woods behind my house then i go to home depot or lowes to get some sand to mix in with it.
depending on where you live depends on what is in the dirt. i dug dirt from outside once. i got home from work and the tank was covered in ants. i dug the dirt while it was still coldish out. ants stayed hidden in the dirt until they heated up and then it was al over. and i checked all around where i was digging for signs of ants. granted it only happened once but i ahve been buying and mixing my own ever since. its cheap enough to do, and id rather have the peice of mind knowing there isnt anything in there.
Perfectly healthy and this guy is a maniac, when you put food near him. Our Croc will gently take food, from tongs but this guy comes at you, like a freight train, when he knows you're holding mice.
I need to get some new pics, of him, in his 6' x 3' x 2' enclosure. I tried to take feeding pics, last night, but he was eating too fast. lol