There are a lot of threads on worming where you can read information about different wormers. Casportpony has a couple of good threads if you do a search for "worming" at the search box top of this page. When 1/2 ml of fenbendazole is used, and repeated in 10days for a 4 pound or 2kg bird, it will usually treat roundworms fine. But to treat other hard to treat worms such as gapeworms and capillary worms it takes a higher dose for up to 5 days. SafeGuard and Panacur are brand names and considered pretty safe.