What I used: Diatomaceous Earth (food grade) It's important to use the food grade!
How it works: It can be sprinkled in the feed, bedding, and outside area where the ducks roam! It is also used against clumps in the feed and against bugs. It is a good preventative against mites and lice and other creepy crawlers that can cause harm to your beloved ducks! When used in the bedding it helps with moisture that can occur on the bottom of it and with the ducks watery poo! With that it helps keep the smell down.
Why does it work: It works because in the DE there are these microscopic cylinders with holes in them, when the bugs move across the DE these razor sharp cylinders cut threw the waxy covering on bugs then the powder gets in the cuts in the waxy covering and dehydrates the bug killing it! It works the same way inside the ducks bodies with internal parasites such as worms. And it does not do any harm to your ducks.
Make sure to use a face mask when applying. People with breathing problems like asthma (like me) will have attacks from it! I thought I would be fine until the wind blew it into my face. Terrible! And it's always better to be safe then sorry!
Invermectin and Safeguard are 2 names I have heard many times in the worming world. More so the Invermectin. Invermectin has a broad spectrum use and is safe for your ducks!