It was a fellow boer keeper who does it, says that what he was told to do, floaters are the parasites not feeding at the time of treatment (it's a couple of years since this was discussed, may be slightly wrong on the feeding bit).
Agricultural merchant sold me Rycoben as a change from noromectin, as I'm also treating sheep, never thought of consulting with vet. As I can't rotate grazing, I'm presuming they needed treating, missed treating ewe after lambing, shes a bit loose, and her female lamb isnt doing as well as she should be, seems fit otherwise. Hoping to get them on fresh grazing soon.