Cocos substrate 2 liter
The most popular substrate material for ants because of it's water-retention capabilities. Sold as solid 'peat' blocks, just soak it in water to loosen it up and make itl expand enormously.
Hempfiber substrate 200 gram
This coarse substrate is favored for nest building by ants like Polyrhachis dives and Formica rufa. It's also a clean option for a natural outworld substrate layer.
Clean sand substrate 400ml
With a simple 'test-tube-in-a-box' setup it's often not a bad idea to add a thin layer of clear sand, adding benefits like ease of cleaning, stability and helping out the ants in some ways.