Most ants should start to dig into sand and soil after one day. Only certain species are able to dig into gel habitats. Making small holes with a toothpick in the sand/soil/gel surface helps start digging. Making sure that the sand/soil is moist also encourages digging, dry sand/soil is hard for ants to dig. If there is still no digging after a few days, try placing a few drops of sugar water onto the sand soil surface.