Invert?

i think its a species of macro algea

if the grean is feathery its a tube worm probably

The tip is feathery, kinda like a green Q-Tip! Its been growing steadily since it appeared and never retracts, just gets longer.

Turns out that its a macro algae...neomeris annulata (thanks Caesar)...its harmless. Also called Spindleweed, its photosynthetic and supposedly a good indicator of your calcium levels.

looks like an arm of a kung-fu fighter with snake tech. lol..

it is a macro algae. It is called shaving brush at www.drsforstersmith.com ... i think

I had the exact same stuff in my tank and couldn't figure out what it was