Greek Tortoise Substrate!

[Vitality]

Time and time again we all find ways to make living for our shelled companions a lot more enjoyable for the tortoise and the owner. The main question, The right substrate? I currently use mainly Eco Earth's Loose Coconut Fiber and sprinkle Repti Bark across the substrate to keep it a little heavy under his feet. When I switched to the coconut fiber my tortoise became a lot more active but I do heed warnings of sometimes getting in your tort's eyes as Greeks like to burrow. So I would like to ask everyone, for an indoor enclosure, what is the best substrate for a Golden Greek Tortoise? I would like claims and reasons for your answers.