I think corals are more agressive then the worm, at any rate that is why we use chemical filtration (carbon, and other absorbents)

I've seen ginormous spagetti worms on the internet...

Yes they do. THey kind of feel around and stick to debri on the sand and pull it in as other say. i grabbed one piece before and as soon as I did that they all pulled in but didnt stop this thing from coming back.

A worm this big wont hurt fish or inverts will it?

lol - Ginormous, love that word ;)

And yeah - they're kosher. I started with a few, and freaked out (I actually pulled a few from the rock when I first saw them) but they've multipled and do great things to clear off the substrate. Heck, even cleaned up a dead hermit crab for me :)

As they multiply, they'll start looking more and more strange, you'll see big pockets of "thread" - but be assured, the stuff is GOOD! :)

Thank you Very Much Everyone.
It is cool to watch. and now I found a slug? well After research I found it to be a STOMATELLA VARIA. I have 2
Man so much stuff to be found AFTER setting up the tank.

I have some and they are brown with bright blue striped "arms"
I think I just have one but their is like 60 little arms coming out of the little whole in the rock!