White flat worm?

[Proteus]

Came home from work today and saw a white flat worm. It was about 1 cm. I pulled it out. Haven't seen any others. And have no idea where it came from

Are they good/bad.

I did read that they eat red and brown flat worms along with various pods but would like your expertise.

Thanks

[Dearth]

Can't help with the reef safe part but been using this link as a guide might help

http://www.extreme-aquatics.com/707/saltwater/how-to-indentify-worms-in-your-reef-aquarium/