Im not basing my oppinion on anything except over 20 years of experience keeping and breeding a large collection of snakes. Im just going to give one of my many experiences with aspen. I have a vet who visits me every 2 weeks to buy rodents and last year i had a guy who has a pretty extensive collection come by and brought 2 of his snakes over to meet with the vet. He was having issues with the animals not passing fecal waste. The vet examined the snakes and we immediatlly put them under the sonogram. Both had large intestinal blockages that were caused by aspen bedding. Every time the snakes ate they ingested small amounts of aspen and it collected. Another issue was one of the snakes was showing signs of a resp issue. After further examination the snake was so filled with a mixture of dust and slime also from the aspen. The vet set him up with an appointment the next day and was able to save one of the snakes but the other died. Now here is the grand finale the snake that died was a spider super stripe. We are talking a 7000 dollar animal. Now im not arguing that people dont have good experiences with it but that is one example of what can happen with the stuff. Now yes cypress is messy but any organic substrate will get in the water. But cypress is a wood that grows in swamps. It doesnt mold like aspen or pine. Paper is super easy and if your not cleaning your tubs when you clean then your not taking to good care of the snakes habitat and opening the door to alot of things. It takes me and 2 guys 3 to 4 hours to clean my collection every week and i take great care in how my animals live. I have animals worth alot of money and it takes alot of work to protect my investment. If you choose to use aspen then i wish you all the luck. Im just giving my oppinion based on experience.