I'm keeping and breeding mine for about five years know. I never cleaned anything (besides the walls of the plastic box), only filled up some soil and put some more bark pieces on top. My banana roaches have about 12 inches (30 cm) natural soil from broad-leaved forest with much microorganisms, springtails, earthworms etc. inside. Food is only given as much as they can eat in some days. There's nothing to clean, no food leftovers (= no fungi) and it doesn't smell at all. Banana roaches will not breed in boxes without soil.