It seems the general consensus is pine 😂😂 I have a huge bag of aspen that I use for my snakes, would that be an acceptable substitute? I love the way pine and aspen shavings smell. I noticed when I had my first rat that it really helped with odor, but she was restless and itchy until we switched. The girls are on paper now and they sneeze all the time. Me thinks it has something to do with how dusty it is 😧