Bioactive substrate: how much, how deep, what mix
A living enclosure is soil, plants and a cleanup crew working together. Getting the amount right is simple arithmetic.
How much
Substrate is sold by the quart. Multiply the floor length by the depth (front to back) by the substrate depth, all in inches: that is the volume in cubic inches. Divide it by 57.75 for the quarts on the bag. Buy a little more than it says: soil settles after the first misting.
How deep
Most species do well on 3 to 4 in. Burrowers (hognose snakes, blue tongue skinks, tortoises, tegus) want 6 in or more so their burrows hold.
Drainage, for tropical setups
Tropical enclosures stay damp, so water needs somewhere to go: 1.5 to 2 in of clay balls on the floor, covered by a mesh barrier so the soil does not sink into them. Arid setups skip the drainage layer.
The mix
- Arid: organic topsoil and play sand, with some clay so burrows hold. Dry on top, a little damp deep down.
- Temperate: topsoil, coco fiber and some sand, with leaf litter.
- Tropical: topsoil, coco fiber, orchid bark and sphagnum, kept damp but never wet, with leaf litter.
The cleanup crew
Isopods and springtails eat waste and mold. Match the isopod to the climate (powder blues for arid, dwarf whites for tropical), add them under bark at the cool end, and give them leaf litter to eat. Let the enclosure run for one to two weeks before the animal moves in.
Your setup plan counts the quarts, the drainage and the plants for your floor, and puts them in the build in order.