This...This is so true about rats as well. I used to breed and have a pretty big colony (12 adults) but maintaining their cage was difficult... and it would smell after just a few days, even with using a litter box and good bedding. I am down to 2 adults now and don't plan on breeding anymore due to the amount of time it takes to maintain them and the odor. I tried using racks, but that didn't work for me or the rats.