I use Diatomaceous earth. There are a few here who are uncertain of its worthiness, but i'll tell you something.
I read about it being a wormer and, when I bought Bella, a puppy, she was very bloated, so I decided to give it a try -- couldn't hurt right? 3 days of mixing a tablespoon into her food a day and she was eliminating long strings of worms, then chunks, then balls of dead worms. This went on for about a week before it cleared up and I kept her on the DE for 14 days to make sure everything had been pushed out. I mix it into the feed here regularly for 2 weeks at a time, and i try to give it to the otudoor cats often.
It works for me, I've seen it work. AND the chickens LOVE to dustbathe in it. Put a box of it in the middle of the coop and they'll dust themselves AND the coop while eating all they please.