digitate hydroids?

[BlueAbyss]

I have a few of these here and there in my tank... I have noted that when the 'stingers' or whatever are dragged across my zoas, they don't seem to do any damage (or even bother the zoas). I don't have any SPS or LPS at the moment though, so I can't say if they would be bothered by them.

Are digitate hydroids much of a threat? Or do they just irritate corals? I have a few of the normal type and I know for sure that zoas don't like being within a half inch of those.