Hitchhiker with hermit crabs - Flatworm?

[Steverd]

Can you ID this critter? It was inside a bag with assorted hermit crabs.
Shipped from a sell in Florida this morning. It is about 1/2 inch.
Is it a type of flat worm? Is it dangerous for my frag tank?
Man, now I want to soak my snails/crabs in some before adding
to my tank. I have Revive, Flatworm Exit and Coral Pro RX.
Are any of these Cerith snail and hermit crab safe?

Thank you

 

[nautical_nathaniel]

None of those dips are safe for your critters, they're designed to imobilize and kill small crustaceans. The best you could do is put them in a QT system for a while and look foot more hitchhikers until you're sure there is nothing dangerous in the group.

As for the unknown critter, it looks like some sort of flatworm to me, I would keep it out of the frags tank just to be safe

 

[reef lover]

Thats a weird one... #reefsquad any ideas?

 

[Lovemyreef2015]

Could be a type of polyclad flatworm. Hard to tell. Do you still have it? If so can you put it in container with tank water so we can see it stretched out please.

 

[KJ]

Headshield slug?

 

[Steverd]

I did put in some tank water. I think it died.
Here's another photo. It's about 1/2inch lone