and the winner is: NEWSPAPER UNDER INDENTED KRAFT PAPER very absorbent easy to clean not messy like aspen and no risk of impaction. I have to admit I feel kind of stupid because I have been using the above for twenty years and just recently switched to aspen because I wanted a more "natural look". I got really worried after witnessing my snakes eat a lot of aspen with their meals. I realized that I should do what is better for my snakes and not what is better for my "natural look" so I switched back to my favorite substrate of all times: THE INDENTED KRAFT PAPER WITH NEWSPAPER COMBO.