Well, I've never seen the marks flatworms left, but I'll make sure to bank this photo in my memory. Pick up a 6line Wrasse he/she will love to rid that problem for you.
I have a 6-line wrasse. He ignores the spots.
Are we sure that they are flat worms. They are awfully....ummmmm.....flat.
Does anyone have a comparison picture?
I'll take more pics tonight.