You'll need to adjust your care and substrate choice based on your tortoise species, type of indoor setup, room humidity and temperature level, and your local area's temperature and humidity. There is no one best substrate that works for everyone.aution! Accidental substrate ingestion with food and (possible) following impaction is a danger with ALL loose substrates, but especially with sand because it's heavy and can collect in the intestinal tract. You should exercise care to keep your tortoise's food substrate free regardless of what substrate you choose.