On the contrary of this belief, it is not I'm possible to house a reptile/ monitor in a glass cage. I have been housing a Colombian Red Tail Boa in Glass, Screen Top cages ever since I have had her which is going on for about a year now. Now it does require a bit more attention but it is very much possible. I have hygrometers in each cage I have for my reptiles and the humidity levels are monitored closely by me on a daily basis. I also have been housing my Borneo Blood Python in a Glass cage for the last 4 months. All of my snakes have always had perfect sheds and have never had any health problems and though I have never owned a Monitor before I have see many in Glass, screen top cages. So if you are looking for a cage to keep your reptile in a Glass top is very much a possibility. If it wasn't and could result in death, Company's like Zilla would not manufacture them.