What is this!?

[IntenseImage]

Just saw this on the glass ... Bout an inch long

 

[Dtfnemo]

Some type of flat worm maybe

 

[ca1ore]

What's on the other side?

 

[IntenseImage]

What's on the other side?

Looks the same, no shell or anything to define

 

[Tahoe61]

You should remove it. Looks like it could be a Polyclad worm, predatory to snails and clams, with reports of them eating Euphyllia.

 

[ca1ore]

Looks the same, no shell or anything to define

OK, so that means not a snail and not a nudi. Agree that it's some kind of polyclad worm. probably best to remove it.