Orchid has great antimicrobial properties for substrate

[Stoneman]

In addition to how the bark is great for retaining humidity, waking on, difficult and mostly harmless to eat because of the large chunks, is easy to burrow in, this article experiments and concludes that it has excellent antimicrobial properties, to help keep your tortoise healthy.

https://www.biovac.ceva.com/en/Reagents/Avian-reagent/Salmonella