Hey all, I am a brand new reefer and have just set up my first reef tank (WB Cube 20). I picked up some live rock from a local reefer to help seed the tank and after a couple days I have noticed there are these tiny white, translucent fans/tentacles sprouting out of tubes stuck to some of the rock (about 1-3mm in length). I have been searching high and low for a definitive answer as to what they are. I have a hunch they are some form of hydroid, although I really hope not. I stuck a clothes hanger in my tank to prod them and the tentacled portion closes up when touched then immediately re-opens. If they are indeed some type of pest what are my options? As of right now I have no livestock in my tank. Attached are a couple pictures, I did the best I could given the size of these things. Thank you for you time!
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