I second all the above. As long as they don't appear to be dirty they are probably cleaner then your door nob. I get my own from the super market and I never had mold or any other sort of harm to my colonies. you can also use toilet paper rolls and paper towel rolls as well. (the center card board part). Above everything they seem to prefer these. I guess they just feel safer in these. But it might take you a while to build up a good supply. I have even had my roaches eat the egg crates due to too much moisture but it did them no harm. This occurred in my breeder bin, of course i don't feed off my breeders so none were fed to my frogs. you can also make things out of card board if you really want to get involved all my dry foods are served out of small card board boxes that i made with a hot glue gun. Cheap and very accessible.