If you are building a moss terrarium, you'll need soil for the mosses. This product includes a lightweight terrarium blend soil mix and is the best
SuperMoss Sphagnum Moss
Terrarium Substrate & Soil: The Most Complete Guide
Propagation Class-Solano Comm. College - Under the Solano Sun
Used to retain moisture in plant soil, beautify indoor and outdoor container plants, improve plant drainage and create water and fountain designs. Ideal for terrariums, dish gardens and various craft and decorative uses. Packed in 5 lb. bags.
Mosser Lee Black Soil Cover Sand
Bloomin' Soil
Compressed Sphagnum Peat Moss - 2.2 cu. ft. at Menards®
Terrarium Moss: The Secret to a Vibrant Terrarium
Sphagnum Peat Moss - Soil Base
Miracle-Gro Sphagnum Peat Moss Soil 85278430 - The Home Depot