Hi, for a while there I had that same problem and this was my experiance. it wasn't the cage that smelled it was the room!! i had a buera and they could go under it and it turns out that they had been going to the bathroom under there and i hadn't known it. my ferret room is my bedroom so what i did was took everything out, ripped up the carpet, and put down a linoleum floor. everything in the room was cleaned and i wash the floor once every 4 days. plus, i change their litter box every other day, and wash ttheir bedding (in my case 2 flannel sheets) every 3 days. last, i use Marshall biodor (so far i haven't noticed a change, but i've only been using it for 3 weeks) now they barely smell at all!!! [Posted in FML issue 3446]