I don't keep as many rats just 10 although they do smell when I don't change them 2x a week. They are in a locked bathroom with a fan and a window LOL! I also have just one male so it cuts the stink. I honestly would take 100 rats to + the smell of 20 mice. I had just 6 and they stank soo bad I killed them off and now have dwarf hamsters in the cage!