Hi Stephanie.  I have never used any commercial wormers but follow a kind of organic health plan.  My birds are healthy and have  a good area to roam in.  I go for grated carrots and some garlic grated into their food.  Lots of sites recommend pumpkin seeds and apple cider vinegar in their water.

I copied this from a site that only uses organic health medicines.  I'm not sure about the waxing of the moon, but Fiona might agree with it.

"Severe infestations of parasitic worms cause loss of feathers, dull eyes, reduced appetites increased thirsts and blood-stained discharges. Prevention is preferable and can be achieved by avoiding over-crowding; rotation of locations and a diet which includes boiled nettles and fresh or sour milk. If treatment is necessary it is said to be most effective when administered when the moon is waxing. The preferred remedy is crushed garlic in water; others include leaves from horseradish, elder, rue, hyssop, brambles and white cedar; onions, cooked or grated carrots, wormwood tips, tansy flowers and mustard, nasturtium and pumpkin seeds. Apple cider vinegar in the drinking water is also effective."

Hope this is of some help to you. Good luck with your flock.

I am glad you put that Danuta as I never used to worm my chickens when we had them but we used to move them around our plot on a regular basis as they were in an ark. Confined yes but to far greater area than if they were kept as battery hens. Seemed to work okay.