It has to be food grade diatomaceous earth, DO NOT eat the kind they use in swimming pools.
Google it... food grade diatomaceous earth, can be found in various places depending where you live... ranchers use it with cattle, you can get a good price buying in volume from one of those sources. And you will use it, love it, so don't be afriad of buying 10 or 20 pounds.
Just start with a 1/2 teaspoon a day and work up to a tablespoon per day at most should do the trick.