When I had 20 snakes in tubs on paper towels it seemed like every day I had at least one go to the bathroom and I could smell it when I walked into the room. Since I've changed to a coconut husk substrate I don't smell it at all, at least until I open up the tubs (I check them all now every morning). My retic smells the worst, her poop is as big as my St. Bernard's poop! And when she pees I can smell it too, but she is on coconut husk and it tames the smell down, but usually that's the only one I can smell now walking in the room. She is about a 30 pound snake. I change out all my substrate once a month, but my retic could use it every two weeks.