Please identify!

[Mario54]

Have these things all over tank? Anybody have a clue what they are? Are they harmful? How can I get rid of them?

Thanks in advance!

 

[Reefing Madness]

Neomeris Annulata
http://www.melevsreef.com/critters/neomeris-annulata

 

[Rob Lion]

I had these in my tank a few months ago, hitchhiked in on some live rock.
They are a pretty looking pest, that can multiply quickly and grow quite quickly too. Nothing in your tank will eat them. They are calcareous and will consume calcium and dkH from your tank.
You can not just scrape them off your rock, they just come back again. The only way I finally removed them for good was to dip the live rock (after removing what i could) in a 50% Hydrogen Peroxide (3%) and 50% RODI bath for 24 hours. This killed EVERYTHING on the live rock and turned it to pure white dead rock after I re-cured it for a week in salt water.