you can do a search for de on this site, a lot of threads will come up. It is Diatomaceous earth. Some people use it in their coops for insect control, it is sharp and cuts and dries up insect bodies. You have to be careful about breathing it, it is a powder and can cause silicosis. There are two different types, food grade and the type that is used by pool filters. The jury is out, read as much as you can and decide if you want to use it or not. Here is a pretty good counter argument to using it ....