I've found I can get diatomaceous earth around here but it's pool grade for swimming pool filters. According to one page I found, it won't kill bugs because it's been heat-treated (calcined) to form larger clumps, so it's not small enough to kill the bugs. Anyone using it? If it's not the right stuff, does anyone know any good sources of food grade D.E.? Because the stuff is very hard to find where I am.