You can use netting to hold them (lightly) to a piece of rubble or plug. They will attach themselves given time and proper conditions. I'd be more concerned with how or why they broke off to avoid this happening again.
hi they got sucked up a powerhead as its grown we didnt realise how close to the powerhead it had got it has now be repositioned in the tank so it doesnt happen again
Aha! That would do it I suppose. If they're growing that well, they should recover nicely for you. The below may help, but I'd wait on someone with more experience fragging and attaching them. I've only watched it being done, I haven't needed to do it myself yet.
