what are these brown fuzzy things

I have them in my tank and they dont seem to bother anything. I have yet to find an easy way to get rid of them. Tried aiptasia X and they came back. Also tried smothering them in super glue, that seemed to work but them I had an ungly piece of super glue on the rock. lol

 

+1 Colonial hydroids
You may not notice the stinging and killing but your other corals will not be able to expand into colonial hydroids. Additionally colonial hydroids will expand into your other corals and push them back. Colonial hydroids do sting and are aggressive however their stings do not always kill mostly just keep at bay, and expand their territory aggressivly and quickly.
If you only have the one rock, I would personally make attempts to chip the rock and free your corals from it and then boil the rock with only colonial hydroids on it. returning the rock and glueing the frags back on.