I bought my DE at Home Depot. It's crushed to the right size for pools and it is called Pool Time D.E. Filter Powder. It came in a 25lb box and it will last forever. It think I paid around 20 bucks for it. Don't get the smaller bags, they may also contain cellulose and you don't want that. That may be what your pool atore has. Avoid it! Here's a pic of what I use: http://www.pooltime.com/mp/v/index.j...053d7010aRCRD&