Are these "sweeper tentacles" from the favia/favites

[Klatzy]

I have a favia (at least I think it's a favia) growing near a zoa (favia left hand side, zoa on the right). There are a bunch of fine white "tendrils" that appear to extend from the favia and down along the side of the rock. They now appear to be on the zoa itself. Are these coming from the favia; are they "sweeper tentacles"? And are they going to sting that zoa, should I move it. They don't appear to retract or extend so I'm not sure they are sweepers, although they do appear to have originated from the favia.

 

[jhuynh]

thinking hydroids. can you look up "digitate hydroids" and see if its the same?

 

[Klatzy]

Hmm maybe they are hydroids. Are these something to worry about, should I consider manual removal? They apparently can sting zoas in particular (and maybe the favia there).

 

[Kensington Reefer]

Look like hydroids
They need to go!
Take rock out and brush them off with a stiff brush
They sting...everything...especially the things you’re trying to grow

 

[tankguy]

if they were sweepers you'd see them coming from the coral. Some can extend a good distance and zap what ever is in reach. Not the case here