I use news paper because my house is very dry and spilling water or pouring water on it keeps my humidity just right. I use like 3-5 pages per 28qt and about 10 in the 41 qt's so urine doesnt't seem to get all over the tub, but still covers a lot of it. I wish aspen was more affordable and didn't mold, i'd use it more for sure. I tried cypress for a while and i'll have to say it was my favorite. humidity stayed perfect with weekly watering, easy spot clean, snakes loved it and were very calm, and it smells nice to me. Just did't like the cost or the possiblity of mites. so newsprint for me.