Flatworms?

[dhanking]

So I saw this little red thing on the glass and it moves, it is alive, and very small( about a millimeter). I have only seen something like this once before on the glass and this is the second time. Is this a harmful flatworm? If so what are the next steps I should take? I would like these questions to be answered. The picture is down below. I appreciate the help. Side note: The worm had a u shaped tail on the glass. It moves very fast for a worm. It balled up out of water.

 

[shwareefer]

Can't figure out what to look at on the glass but i don't see any flatworms. The spec center frame of the white dish does not look like a flatworm either.