hi guys ,i am building a new outdoor enclosure for 4 of my star tortoise, but my mother in law use some insect control on the soil , i already took most of the soil out,but there must have some left there, so i am think getting some substrates cover it , so what is the best out door substrates ? and i am worry that they will dig so they may still have contact to those soil.any advise will be great . thanks