Help ID this stuff.

[Alberta-newb]

Oh the horror! Your pictures really brought back some bad memories for me. Indeed, jump on this right away and go for a natural approach. I waited far too long on my tank. Since wrasses are a no go for me (I eventually will be getting mandarins) I went with the "chemical warfare" route. Tank is flatworm free for 2 months now (as far as I can see) but I believe it did contribute to the loss of my rabbit fish The population got really out of control in a matter of a few weeks.

Great photo quality BTW, as Keri said we should create a "bad hitchiker sticky" and include these pics.

Francis