What sort of substrate would you recommend for a tortoise who will be kept indoors for the winter? I am looking for something that is commercially available (say at Petco, Pet Smart, Pet Supplies plus..).
It really depends upon what kind of tortoise it is. A redfoot requires a more moist substrate while a desert-type tortoise needs a little humidity, but requires a drier environment. There are many choices, but I like to use orchid bark or cypress mulch. For the desert-type tortoises you can moisten it occasionally so that it stays a bit damp underneath but not on top, and for my Yellowfoots I can keep it a little wetter. The orchid bark or cypress mulch doesn't get sour-smelling, however, it does allow little creepy crawlies to grow on it and has to be changed out about once a month. The bugs aren't harmful to the tortoise, but I don't like seeing them crawling all over the substrate. Someone said that spagnum moss deters the bugs, but I haven't gotten around to trying it yet.