I personally don't use anything on the bottom of my cage because it has a white plastic bottom, my cages are surrounded with lush tropical landscape both inside and out so substrate or paper towels get wet and dirty too quickly for me to keep up with, instead, I cut a small hole in the corner of the cage very low so my chameleon can't escape, and every few days or so I'll blast all the poooooo and dead crix out the corner with the hose, and about once ever 2-3 weeks, I take my came out and scrub his cage and vertical playpen down with mild soap and diluted bleach.