I'm dealing with them now too. They are near to impossible to eradicate, and bhanson is correct. Torching them is about thr only way to get rid of them. Unfortunately some of mine have decided to pop up in a colony of mint chocolate chip zoos.
Mine got outcompeted for space by some Tubipora musica.
Are they already a big problem? If they're not spreading, I'd almost be tempted to leave them (though following SM's experience, that may be a bad idea).
I have hydroids and they are not really bothering anything. However, if they do, just light then up with some kalk paste just like you would to a aiptasia anemone.