Friend Or Foe?

[richard t]

Hi
I've just spotted a new tank inhabitant stuck to the glass on the front of my tank. It's about 2cm in diameter, almost transparent, seems to have central mouth parts and moved when touched. What is it? Can't get a pic as the camera won't focus. By the way it's wafer thin.
Any ideas?

 

[Opcn]

Is it like a disk or like a flatworm?

 

[Chac]

Have a look on here Xtralreef & see if you can spot it