Flatworm ID needed - tan with white line

[The Life Aquatic]

I unfortunately have these guys on some euphalyia. They seem to only stay on the polyps, I haven’t seen any on the base or flesh (they retreated there when I dipped, in the second photo). They are a tan/brown with a distinct white line and they are small.

 

[shakacuz]

if they were on a euphyllia i would instantly assume they're predatory flatworm(euphillya eating flatworm - EEFW)

 

[WalkerLoves_TheOcean]

Yeah, I am 99% sure those are euphillya eating flatworms.