Choosing the correct substrate for tortoise is in our opinion crucial for the well being of your tortoise. 
I often see tortoise kept on pellets, bark chips, sand, woodchips and even specially produced substrates which are labelled for tortoise. 
However these are far from ideal. Tortoise kept on those substrates do not act how they should and can be lethargic etc. This is sometimes the fault of a pet shop or previous keeper giving bad advice. Weve seen countless of times tortoise behaviour change for the good when moved to this. It promotes natural behaviours such as digging/ burrowing.
 
 
 
We find our females love nesting in this substrate. 
 
We mix this ourself. We Only quality sterilised soil is used with no pesticides/ fertilisers this then is mixed with coco coir. The reason it why we mix with coir is soil alone dries out very quickly and becomes dusty (not ideal for tortoise) Can lead to respiritory problems and eye. Dust goes everywhere when soil is dry. 
The coir retains moisture which keeps soil pliable. We recommend you churn it up every couple of days and add water i.e mist not soak. The ideal consistency is a crumbly texture.
This is especially good with younger hatchlings as it keeps humidity in the substrate which is known to reduce pyramiding. Our Hatchlings bury themselves completely and emerge in the morning. Which is a totally natural Behaviour
 
The soil is also dosed with calcium for those who grow plants in your setups (Makes it calcium rich)
 
 
This mix is our own mix and is bagged and sealed fresh.It helps create a great microclimate.
It has also been used in terrariums with Amphibians and bio active setups.