Flatworm?

[Jaag]

So I just saw these guys on my glass as I was cleaning it today. They are not brown or red so I felt a little better but can someone help me out with an id on them and let me know what are the next steps?
Thank you

 

[Big G]

Good guy: Ghost Flatworm. Their populations will grow responding to the conditions in your tank they like and then kinda just disappear.