Hi,
I bought some Diatom powder that is a bit of a cure all ( well ...kill all actually! ) Its harmless to the birds but kills red mite, lice and aparently if ingested it kills worms. I use it in the coop, on the birds and put it in the garden in the dust baths that the birds create but you can sprinkle it on their pellets as well. I do use Flubenvet but find getting the dosage right for half a dozen bantams pretty tricky. Also I'm never sure that everyone gets their fair share and administering it for seven consecutive days is also difficult unless I dont let my birds free range.
The only time Ive seen them pass a worm is after vermex but again, if I let my girls range they will find other water sources rather than drink the vermex treated water.
Little monkeys!
Buffy