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