PS My dogs are large to extra large, 65 to 125 lbs at ideal weight, and have all lived to 15 or 16 years healthy. My 125 lb Golden Retriever mix lived to 16. It's rare for dogs to live as long as mine, so I'm pretty good at figuring out what's good and effective for their ailments.
Tip: To completely cure symptoms of arthritis in dogs, use the liquid Farnham's Next Level Equine Joint Fluid "For all classes of horses and dogs" from TSC (accept no subsitutes).
I know a little bit about dogs; congrats to your dogs and you for taking good care of them.
The scolex is the head of the tapeworm which embeds itself in the mucosal lining. DE cannot penetrate that deep into the lining. The only way to kill it and prevent it from reproducing white rice-like segments (eventually seen in feces or the rear end of the dog or in fur) is a chemical wormer specifically needed to completely kill the tapeworm. Kill the head, no more segments. The wormer is absorbed into the bloodstream and kills the worm, then it releases it's pincher grip and is absorbed as protein in the digestive tract. Some wormers paralyze worms causing them to release their grip...no more bloodsucking. BTW; each rice-like segment contains hundreds of eggs. Soil/grass remains contaminated with these eggs. Fleas eat the infective eggs, dogs eat the infective fleas when bitten...and the dog gets infected, completing the tapeworms lifecycle. This is known as the indirect lifecycle of cestodes. Same applies for chickens.
DE cannot enter into the bloodstream to kill or paralyze worms, nor to kill the head. The same is true for capillary worms, gapeworm, eyeworm, gizzard worm, cecal and large roundworms.