I use Repti-Bark (Zoomed, I think). Looks very natural, very low dust, no strong odor. I didn't think they'd be able to burrow in it but they do! It supposedly lasts 6-12 months. You just take it out every 2 months or so and give it a nice long soak in warm water, let dry, and put back in. I want to say it was around $15 for an 8 qt bag? So extremly cost efficient. I was able to do a fairly deep layer in two ten gal's and a five gal.