Digging box substrate?

[dystopoly]

I've noticed my new 3yo girl digging at her carpet a lot, and while I'm against using sand as a substrate for the ENTIRE tank - I want to provide her with a digging box so that she's able to dig around and bury herself like she seems to be doing with the towel that im using at the moment to simulate having something for her to hide under. However, I'm not entirely sure what kind of substrate I should be using. I've heard of using play sand - but specifically I've been looking at these two substrates off amazon:
http://www.amazon.com/gp/product/B000N5OM8S/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

http://www.amazon.com/Zoo-Med-ReptiSand%C2%AE-Pounds-Desert/dp/B0002DIZKC/ref=sr_1_1?ie=UTF8&qid=1434310366&sr=8-1&keywords=reptisand

One is meant for holding its shape, and the other is plain old sand. Since she is a female, I know that she's going to be laying some infertile eggs eventually - but I wasn't sure whether or not to go for the shape-holding sand just for a digging box for general use or not. Any input on this? Also, if these brands are known to be problematic, do you have any other suggestions for substrate?

 

[CooperDragon]

The most common setups I hear about include an external dig box that consists of a combination of moist play sand and soil that will hold it's shape when it's made into a tunnel. Once the substrate is together, dig a small starter tunnel and let her finish it up. As long as it's stable it should do the job. From the photos I've seen, prepare to give her a nice bath afterwards =)

 

[Taterbug]

Are you sure she isn't trying to lay eggs now? If so, for a normal digbox I'd use a soil mix or maybe something like dried leaves if you feel more comfortable with that. I've also used alfalfa pellets.