What's this in my zoa?

[comino]

First of all: Hello everybody! Im new here

I have new 250 liters (50g) aquarium for 2 months now.
Inside there are only few corals... some palythoa, mushrooms and zoanthus.

Last few days I've noticed something "strange" on zoa colony.
Some worm like creature is moving around but it's attached to one spot on stone with his backside. And at night the creature strech itself to about 7cm long (3").
Also I've noticed one polyp is dead or soon to be. Polyp has something like a white sore and it's movig too much like it's not attached to base.
Oh... and also I've noticed white spots on my zoa colony running arround polyps.

Can anyone help me? What's that worm like creature? Is it good or bad? If it's bad how can i remove it?
Thank you! :fish1:
I hope you can understand my english also :rollface:

So here are movies and pix Ive took:
http://www.youtube.com/watch?v=k1XvjyX-BFQ&feature=channel <- "worm" in daytime and polyp
http://www.youtube.com/watch?v=fwjx10iDjZE&feature=channel <- worm at night

 

[comino]

Ah... and pix:
Polyp:

White spots:

"Worm":

 

[DaddyReefer12]

If you Take the Zoas out and DIP them in REVIVE what ever it is will DIE. Any time I get new Zoas I always DIP them to try and get rid of any pests.

 

[zoadude]

No clue but FlatWormExit, dipping them in it, a couple drops per quart of tank water in a bucket or bag, for 20 minutes, will kill everything except the zoas.

 

[ajger]

It looks like a digitate hydroid, I've heard they will sting nearby corals. I had them starting to over run my tank shortly after it was first setup and picked up a couple of peppermint shrimp which took care of them.