are these bad or harmless flatworms?

[JonReefer]

So i got a group of these on the one side of tank on the glass..are these harmless or are they an issue I should worry about.

 

[Elysia]

I know people who actually like them! I had one crawl on a seahorse once, and the seahorse didn't appreciate it at all. I have read that they eat copepods, so I usually try to siphon them out. Its not as though they have huge appetites... Its personal preference, I guess. They aren't going to hurt anything besides a few 'pods.

 

[Airwolf75]

Looks like a regular commensal flatworm to me.