Diatomaceous Earth works by slicing through the exoskeletons of parasites. But flies are a fair bit more meatier than parasitic worms, so I'm not sure Diatomaceous Earth would work against flies. You also need to be careful with handling Diatomaceous Earth - as it's VERY dusty. It does the job for de-worming, but you can't expose yourself, or your pet to it everyday. 2 - 3 times a week max, I think, but not even humans can handle its dust every day, nor should they.
Diatomaceous Earth are actually fossilized sea plants. Breathing in the dust doesn't *technically* do any harm, but it's recommended to not be breathing it in every day.
In fact, I think a better suggestion would be to sprinkle the DE36 directly into the litter box, or wherever they do their business. Not in the food bowl - rabbits shove their faces into their food bowl, and I imagine the DE36 would risk causing more of a harm in the food bowl and on the food, than in the litter box.
Last edited by FlickeringHope; 02-25-2010 at 11:06 PM.