I use several wormers; wazine, valbazen, safeguard, pyrantel pamoate and I worm monthly. I havnt had to deal with tapeworms since moving to Jacksonville 6 years ago. But Equimax is readily available in feed stores around here if I need it.
My BR's have been eating small snails in shells due to...
Free ranging really doesnt have anything to do with it.
Tapeworms have an indirect lifecycle. A chicken would have to eat an infected insect in order to get tapeworms. Even if your birds were penned, a chicken will eat any bug that wonders into the chicken pen. Flies, termites, earthworms, and...
Get some Equimax at your feed store, it'll be in the equine section. Dose each bird orally with a regular pea size amount of the paste. You can put it on a piece of bread and give a piece to each chicken. Repeat dosing in 10 days.