Ok wow that's good to know, that might be it actually because I thought they didn't like the substrate because they'd crawl around on top n roar like little dinosaurs is what it looked like but you just cant hear their roar cuz their little. But yea I have them on the same stuff as my Japanese rhino (rotting ground cover I gathered around an oak tree) n he just goes nuts munching through it n he practicaly doubled in size in only a month! but he also loves snuggling down by the heat pad so that's interesting. Thanks a lot guys what a twist!