Calcium bentonite is clay left after volcanic eruption. It contains calcium, magnesium, sodium, and other trace minerals. It won't hurt them.
As to DE, there is legitimate concern that it is harmful for chickens to breathe. Birds have very sensitive lungs, and DE is a known respiratory irritant (for both man and beast) due to the silica content. Food grade is better as it has the less harmful type of silica in greater number but still contains the more troublesome type as well. (Pool grade is the worst for inhalation).
DE has very sketchy results as a dewormer. Some studies showed slight worm load improvement in birds who ate DE. Other studies showed birds who ate DE had a heavier worm load.
To remain effective for external parasites, it should remain dry, but that also keeps it air borne. It also has had very mixed results for effectiveness for external parasites.
If you do use it, try to keep it in places that do not allow for air borne distribution.
Because of the known respiratory risk, I personally prefer to use other things such as permethrin dust in the nesting boxes and on the birds.
For worming, there are far more effective things than DE. If you want a preventative, simply mix up pumpkin seeds with cayenne pepper and garlic. Feed several times a week. That will help purge worms but will not prevent a gradual build up as the worms are left alive to be picked up by the next bird. Organic methods require strict litter management to be effective. I also recommend keeping apple cider vinegar in the water to help keep the gut acidified. That won't kill worms but it helps boost the immune system and overall gut flora that keeps worms in check.
Unfortunately, no herbal will treat a worm build up. Once you've got a build up, worming drugs are necessary. Fenbendazole is coming back onto the market for poultry, and it is an excellent choice for deworming.
But with strict litter management and some regular herbals, and limiting wild life access, drug use can be greatly reduced.
Unfortunately, while nice sounding, DE is likely more harmful than helpful.
My thoughts.
Lofmc
