I've always kept my snakes in glass with screen tops so I'm new to the whole tub deal. It's just two snakes... for now.. (I've got the itch for a few more and designs for a rack!). I've got two sterilite tubs with locking lids, two UTH, and a thermostat. I'm really hesitant about putting the UTH on the bottom of the tubs because I don't want my snakes to get burned. Would putting it on the side of the tub make a good enough hot spot? And what's the best substrate to use in the tubs? I've always used natural looking stuff but that was mostly for appearance.