wish i could help, i know that when those things stick they don't want to come off, why cant the rock go with them? other than that i would be as gentle as possible and try to remove them i wouldnt use a razor or anything like that i know the bodies of the feather duster worms are pretty fragile. Also i dont know if you are aware of this or not, but if you do move them and the feathers fall off, (its actually the filter feeding gills of the worm) the feathers will regenerate in a short period of time usually about 2 wks, but can take longer, they do that as a natural response to stress so if they do come off, dont flush them they may come back, i have witnessed it first hand about a dozen times, also i seen it take as long as 6 wks .