What the duce?.. ID

[dmbreefer]

i found the same thing a yesterday on one of my plugs, i was worried that it could be a flatworm bc, well they looked flat haha, removed a couple of them but i dont think they would be a type of flatworm bc these guys move pretty fast, zip around like a copepod or some other bug...looks like they could be Harpacticoid copepod (2nd picture) on this website http://reefkeeping.com/issues/2003-02/nftt/index.php

 

[scubasteve06]

those look like copepods to me. FWIW

 

[Baltimore Bryan]

I had something that looked very similar in my tank. They were whitish with orange on about half of them- I thought it was some sort of egg sack. They did not move but did spread locally on the glass. If I scraped them with the mag float, they broke off so only a small piece was still left on the glass. They sort of died off in my tank I think, I don't see them anymore (although I don't look for them) and they never harmed anything.
Bryan