I have a perlite drainage layer, separated by a 'weed free' mesh from the home depot. Then I've got about 5" of:
Organic tropical soil
Coco coir fibre
Coco husk
Moss (generic brick moss)
Organic potting soil
Vermiculite
Some rocks
2" layer of moss on top
Buttload of cute little tropical plants for shade, humidity, and aesthetics
African land snails for recycling
And a millipede... somewhere.
I just mixed it all up, added the plants and critters, and badda-bing: Living room jungle.
It looks sorta like this, but the pic is a couple months old.
I have Echo Earth mixed with 15% sand, on one side I have sphag moss on top of the Earth.
I have had Olive on it for a while now and am extremely pleased with it all..
I would be concerned to put down just sand. as when the tort digs down they are eating level with pure sand. Not good. I would rather use the cypress mulch and Sphagnum moss combo or just the sphagnum moss. I put Sphagnum moss about 6 inches deep for an larger 6+ inch tort ( dampen it squeeze out the excess water) place it in the enclosure and place a lid over 3/4 the enclosure and it seems to keep the humidity up fine. Then I mist heavy when needed.
Philippe de Vosjoli promoted an 'bioactive substrate' in the book 'The Art of Keeping Snakes'. In the book, he recommends using layers to better simulate natural conditions. An article based on the idea can be found at www.herpfamily.com/docs/BioActive%20Substrate%20System.doc
The basic idea is:
1. About a 1" layer of coarse rock, like lava rock. This allows a pool of water and holds the bacteria needed to decompose wastes.
2. About a 2-4" layer of soil mix, tailored to the species. For Red-foots, I would combine sand, 'clean' soil (no vermiculite, etc.), some sort of absorbent material (compost, humus, shredded absorbent wood, etc.) Peat or sphagnum moss is pretty acidic- I'd skip it in this layer. This layer is where moisture is made available, and where earthworms, pillbugs, bacteria, etc. break down feces, food wastes, and even the eggs of gnats, etc.
3. A layer of leaves, long-fiber moss, etc. that keeps the top layer from being actually wet.
4. A watering tube in a corner lets you put water in the low layer, which wicks up into the other layers and humidify from the bottom up.
5. Add plants (either in the soil, or in buried pots) for humidity, shade, and food. Add earthworms and pillbugs to help break down wastes, prey on other bugs eggs, and act as snacks.
6. Clean out big wastes and gently stir in other wastes as needed. With tortoises, I suspect we would also have to periodically pull the top layer back and aereate/fluff the soil.
I'm planning to do this in the under-construction almost 10'x4' winter habitat I am building. I'll be posting results as things develop.