ProRep Tortoise Life is the most popular tortoise-specific substrate on the market, created to meet the needs of tortoises originating from arid habitats, particularly Mediterranean and Russian tortoises. It has a 50:50 mix of high-quality loam topsoil and sand, with a little limestone grit added to provide calcium if the substrate is eaten. This mixture simulates the texture and moisture retention characteristics of the soils found in their natural habitats far more closely than many other available substrates.