I have two hatchling Hermann's, and I would suggest keeping yours on paper towels until you've had him at least a few weeks, so you can monitor his urine and fecal output--the paper towels make it really easy to see, even when it's a very small tortoise. Also, if you end up with a worm problem, paper towels are simple to change, making it more likely you'll keep everything clean.
After that, if you want to change substrates, either a mix of topsoil/play sand or aspen works well. I usually use aspen, because my indoor enclosures are in a spot where I can't have the weight of dirt and sand. The torts aren't interested in eating the aspen, and it's easy to make little hills and valleys with it to make their enclosure more stimulating.
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Sohni
Northern California
0.1 Baja de L.A. Rosy Boa
0.1 Okeetee Corn Snake
1.1 Rubber Boas
1.0 Leopard Gecko
0.0.2 Hermann's Tortoises
plus my kids' herps:
0.0.1 California King Snake
1.0 Mexican Rosy Boa
0.1 Leopard Gecko