ID Help Very Strange Night time creature

[erndog1001]

Hey everybody. I'm a huge fan of viewing my tank after the lights go out. I think there's as much to see after dark as during the day. Now I've seen all kinds of strange things crawling around but this one is hands down the strangest I've ever seen yet. Anyways I managed to capture a decent video with my phone and I've posted it to You Tube.
www.youtube.com/watch?v=iBYrDlsSQ60

Here's some history. The tank is new. 375+ gals home made. I got the rock from a kid who had it all in a 90 gal. and it's been in my tank for like 2 days. In the video it appears to be hunting the hermit but i dont think that was the case. I think it was just trying to find a hiding place from my light. Bc when I first spotted it It quickly went up under the closet rock and I moved it to get the video.
Its very flat and fairly large. As you can see in the video its movement was almost amoeba like. I'd say it was 3 1/2 - 4" long and it was at least an inch across.
Anybody got any idea what it is? Thanks all

 

[Whiterabbitrage]

Following

 

[jkoot]

Some sort of nudibranch?

>jason

 

[terrypercula]

Flatworm?

 

[Windirmere]

Its a preditoty flat worm that will eat clams and snails get rid of it

 

[Doogy]

Dang that thing is crazy looking

 

[tektite]

Polyclad flatworm, bad news.

 

[mayjong]

polyclad flatworm most likely.
destroy with extreme prejudice

 

[eferna]

Pericelis Flatworm

or as mayjong said polyclad flatworm.. destroy it, they feed on snails and clams

 

[deleau]

That poor hermit looks scared to death the way it seemed to be backing away...could be from your light but its a better narrative to think its trying to get away from the flatworm.

 

[squishifishi]

Wow, that flatworm is so big!

 

[emict326]

wow

 

[erndog1001]

That poor hermit looks scared to death the way it seemed to be backing away...could be from your light but its a better narrative to think its trying to get away from the flatworm.

Yeah I know right lol The hermit didn't stop either until he was a good foot away from the thing.

 

[erndog1001]

Pericelis Flatworm

or as mayjong said polyclad flatworm.. destroy it, they feed on snails and clams

Aww That really sucks bc I have Derasa clam I intend to put in the tank. Hmmmmmm What if I stick him in my sump? Bc ya gotta admit Its one cool looking animal

 

[tektite]

They can fit through ridiculously small holes. Plus the last thing you need is it getting sucked up into your return pump...magical multiplication LOL!

 

[erndog1001]

Well I guess I have a problem bc I've been down each night since and i haven't seen it again. I guess I'll just wait awhile. Get some cheap snails in there and see what happens

 

[ingtar_shinowa]

They are a very accomplished killer. It will get back into your DT from the sump. you could make a nano tank just for it though.

 

[erndog1001]

Still have not been able to spot this critter again. And the snails I put in a week ago today are doing ok. So I moved my Derasa Clam over today. I read that these worms can be herbivores to. Do you suppose its possible its one of that spieces?

 

[alan.reef]

set trap. to remove asap..if i were you.good luck.

 

[joshPensacola]

catch and dont kill..... put him in a small plastic container in your tank with a snail and see if he eats it. if not after a couple days let him go. pretty cool if he isnt a killer