Substrate is very often a big debate in keeping tortoises. I have Russian tortoises, I try to mimic their natural habitat as closely as possible.Since they are an arid species, I use a 50/50 mixture of playsand and topsoil deep enough for the tortoise to burrow.ubstrate is very often a big debate in keeping tortoises. I have Russian tortoises, I try to mimic their natural habitat as closely as possible.