It's both harmless and effective, developed for poultry and will do the job without passing into the eggs. I'm not sure if it is actually classed as organic, but as all chickens get worms and their health is compromised if they're not dealt with effectively, it's certainly worth considering. Like you, I started out by using Vermex in the days when it did actually claim to kill worms, but some tests were done which demonstrated that it doesn't kill them, although it claims to help balance the chickens system so they can better resist them. So then I decided to spend my money on something that would do the job instead.
You can have a test done to see if they actually need worming, by analysing their poo samples, but I think most people just treat their birds twice a year anyway. With pullets going on to ground not previously used for chickens, the risk is less as there won't be such a buildup of worm eggs ingested via hosts such as earthworms, slugs etc. but when importing new birds you don't know what they may be bringing with the m, and they'll have come from somewhere where the ground has had a lot if poultry on it, perhaps for many years. Regular poo picking helps to beak the cycle as well. Personally I worm any new birds along with my older ones, to keep them all in synch thereafter. Some people never worm their chickens, but a worm burden does pull them down and will lower their productivity and also resistance to any other health challenges they encounter.
Flubenvet powder is easily available over the Internet, from animal sites such as Medicanimal or on Amazon, and a bit of research to compare current prices + postage may be worthwhile if you decide to use it.
