Is this a nudibranch? Or flatworm?

So I pulled a plug out of my sump for my new Jedi Mind Trick And I was about to remove old glue off of it when I saw this. At first glance I thought it was algae, but it then started moving. Fast. I dropped it. I have never had a nudibranch or flatworm or anything like that in my DT/sump, fortunately. Is this this a nudi? If so, is it the bad kind? It is NOT going back in there either way, but chances are ..there are more of them in there, and I'd like to know if I have a problem to deal with. Here are some pics, and a video of it...

 

That is a Polyclad flatworm. Very cool but a predator to snails, clams and possibly some corals. I myself think they are very cool, but not in a mixed reef.

 

Thanks Corailline. Is it possible to get rid of them in a fully stocked tank? Should I even try? Do they target a certain type of coral? I don't have clams, and can easily replace snails if necessary. If they are not too much of a threat then I won't bother taking apart my whole tank to get rid of them...

 

In the past I have removed them and put them in tanks not reef devoted, just because I did not have the heart to kill them. They do love snails, they envelope snails and secret and enzyme as well as suffocate them, if I remember correctly.

An amazing creature in my book but not everyones cup of tea.

I have never had a population get out of control. In over 20 years of reefing I have come across 5.

 

pretty cool!

 

Okay. Your crazy. They creep me out like no other. I keep checking my hands and arms to make sure one isn't on me. They remind me of like a leech or something. Ew. I'm a girl. I've had pet snakes. I play with my brittle star. I'm not afraid to stick my hands in the tank. But that thing? I can't deal with it. Ugh.

Anyway, its good to know that they are controllable. I will remove them if I see more. However, I don't have anywhere else to put them. I can ship them over to you if you'd like! ;D Priority mail.