weird slug/ flatworm thing

[Quash]

So again, as always im oogling at my tank, and I notice some dark thing against the glass in my LS. I take a closer look, this looks like cyano trapped in the LS. I said wtf, then I saw it move. And it moved all along the glass in the LS it was really flat. It was prolly dark purple, and about fuggin an inch an a half to two inches long, in width it was prolly half a cm wide, prolly less, I would say no wider than the Enter or Return type thats on a standard keyboard, just the letters that say Enter not the key, I think thats half a cm. Anyhow, wtf is this, is it good, i went to get my camera, and lost the little fugger

[Dave ESPI]

Species of Bristle worm. Did it have one end darker than the other by chance ?

[Quash]

I didnt think it was a bristle worm since it didnt have any little legs, it was all one color tho