wow...I was just going to post a topic on this very same subject, lol and ping @35ppt
I have been looking at my tank after lights out since I added some bumble bee snails a few weeks back for vermited snails (what a pain) and they only come out after dark. I have a red led flashlight that I use so things do not appear to notice it but I started seeing instances of these tentacle like things coming out and waving about. I only have three that I can see but they appear to hurt SPS, I have some that appear to have irritated spots on the acros. I did some googling and finally identified them to be Digitate hydroids, reefcentral has a good thread on them - Digitate hydroids help? - Reef Central Online Community
some say peppermint shrimp and halloween hermits. I actually have a halloween hermit in this tank so I dunno if they really help or not, but I only have three that I can see.
Would like to see if anyone finds anything that works, right now I am trying to do manual but some of them are buried deep in the rocks and I cannot see where they are coming from...