99.9% of the time it's a bristle worm and I honestly wouldn't even worry about it. If you want to eliminate pests you can go with dry rock or man made base rock. It's really not that hard, don't worry
. With your knowledge of fish keeping and the amount of research you do I have no doubt that you will have a gorgeous reef tank. And once you get it running for a few months it's just going to be a matter of making the water salty
, everything else will be same as your fw
maintenance routines I'm sure.