Diatomaceous earth (DE) is a chalk-like powder composed of the fossilized remains of diatoms, or plankton. DE's main uses are to filter pools and to kill insects. Different grades are used for these two tasks.
As an Insecticide
Buy DE that is marked agricultural-grade, horticultural-grade or food-grade for use as an insecticide. Pool-grade DE has been heat-treated, so some of the silica content has crystallized, creating a breathing hazard, according to Golden Harvest Organics.
Look specifically for 100 percent pure DE (food grade) if a child will be able to play with it or a pet can lick it up; other grades may contain additives that are unsafe for them. Food-grade DE is available at health food stores. If you don't have pets and are using the DE externally only, agricultural- or horticultural-grade DE should suffice.
Try your local garden and hardware stores, but their DE may not be sufficiently pure. If you cannot find food-grade DE locally, try online at one of the links listed in the Resources section of this article.
For a Pool Filter
Buy pool-grade DE if you have a diatomaceous pool filter. Find it at pool supply stores, of course, as well as online. Hardware stores may carry it as well.
Avoid other grades of DE, such at horticultural grade, since pool-grade DE has been heat-treated to make it a more compact filtering material, and is much cheaper per pound than food-grade.
Try wholesalers, since they can get you the best price if your pool is large. Five- to 10-gallon pails are the size needed for a pool.
About this Author
Paul Dohrman's academic background is in physics and economics. He has professional experience as an educator, mortgage consultant, and casualty actuary. His interests include development economics, technology-based charities, and angel investing.