What the substrate needs to do
Use a clean soil-style substrate for Nhandu chromatus that can hold its shape without becoming hard, dusty or permanently waterlogged.
For Nhandu chromatus, the substrate in a Brazilian Red and White Tarantula enclosure should support normal movement and retreat building. Heavy decor must not be able to collapse if the spider digs underneath it.
Depth
Brazilian Red and White Tarantula tarantulas are terrestrial, so give Nhandu chromatus 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 Nhandu chromatus. Small slings and fossorial individuals often use proportionally more depth than a large settled terrestrial adult.
Moisture
For Brazilian Red and White Tarantula tarantulas, maintain moderate moisture in lower substrate with good ventilation and a water dish. 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 Nhandu chromatus 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 Nhandu chromatus does not collapse immediately. The upper surface can remain looser where appropriate.
For Nhandu chromatus, keep rocks, heavy cork and ornaments in a Brazilian Red and White Tarantula enclosure low and secure so excavation cannot undermine them.
When substrate needs replacing
Spot-clean waste and prey remains from the Nhandu chromatus enclosure. Normal digging, webbing or rearrangement by the spider is not a reason to replace clean substrate.
For Nhandu chromatus, replace all substrate for a Brazilian Red and White Tarantula only when it is fouled, contaminated, persistently mouldy or no longer structurally usable.