Please help ID this white snail like work

[sebekuk]

Hi, I have just found this on the glass on my tank. Its white. Over an inch long maybe even 1.5inch. Flat, round. Move fairly quickly on the glass.
Can someone please help and identify it please. Is this planaria? I was thinking they are much smaller.

Thank you.

 

[sebekuk]

Sorry for the typo in the title. I don't know how to edit it. Should say worm.

 

[BloopFish]

Looks to be a flatworm of some sort, could be a type of planaria like you said. Most eat detritus and leftovers, but some can be trouble. Flatworms can come in a variety of shapes and sizes.

 

[Tahoe61]

Could be a Polyclad FW, I would remove as they may feed on snails and clams.