What the substrate needs to do
Use a clean soil-style substrate for Tliltocatl vagans that can hold its shape without becoming hard, dusty or permanently waterlogged.
For Tliltocatl vagans, the substrate in a Mexican Red Rump enclosure should support normal movement and retreat building. Heavy decor must not be able to collapse if the spider digs underneath it.
Depth
Mexican Red Rumps are terrestrial, so give Tliltocatl vagans enough substrate for normal digging while also keeping the fall distance from the lid low. A stable ground-level hide should sit securely on or in the substrate.
Match substrate depth to the current size of Tliltocatl vagans. Small slings and fossorial individuals often use proportionally more depth than a large settled terrestrial adult.
Moisture
For Mexican Red Rumps, keep a water dish available and maintain a modest moisture gradient; avoid persistently wet substrate. Add water in a controlled area and judge how the enclosure changes over several days instead of trying to keep every centimetre equally wet.
Substrate moisture for Tliltocatl vagans should work together with ventilation. Persistent condensation, a stale smell or widespread mould usually means the setup is staying too wet.
Compaction and stability
Press the lower substrate layers firmly enough that a retreat or burrow for Tliltocatl vagans does not collapse immediately. The upper surface can remain looser where appropriate.
For Tliltocatl vagans, keep rocks, heavy cork and ornaments in a Mexican Red Rump enclosure low and secure so excavation cannot undermine them.
When substrate needs replacing
Spot-clean waste and prey remains from the Tliltocatl vagans enclosure. Normal digging, webbing or rearrangement by the spider is not a reason to replace clean substrate.
For Tliltocatl vagans, replace all substrate for a Mexican Red Rump only when it is fouled, contaminated, persistently mouldy or no longer structurally usable.