Worm?

[pat18]

I need some help, when i was looking in my refugium, i saw what i think was a worm, both front and back were yellow, and the center was black, and between the center and each side it is orange.
( yellow--->Orange--->Red--->Black<---Red<---Orange<---Yellow). I was going to take a picture but i do not know where it went now. If anyone could tell me what it is and what i should do about it, it would be very helpful, because don't want anything to go bad. Also it was about 1/2" long.

[bignose]

It's in your refugium I don't think you should have any problems with it.

[Nano]

the best way to tell is a picture even if its a crappy one, it helps a lot more to see the body shape, size, etc. have a look on http://www.chucksaddiction.com/hitchhikers.html
you might be able to find him on there

[pat18]

Thanks for the replies, i went on the link and to me it looks most similar to the Eurythoe complanata, but it was small so it is a little hard to tell