what are these worms and are they harmless?

[tannersmith2000]

Hello

I was examining my glass on my 30 gallon FOWLR and found three different worms on the glass. I placed them under a microscope and would like for someone to identify them.

Thank you
http://youtube.com/watch?v=RCDAvfLyNEQ

https://m.youtube.com/watch?v=A2oIpsg2-l4

https://m.youtube.com/watch?v=37Y8_m4eGBg

 

[Spar]

wish i had an answer, but neat videos nonetheless.

 

[Newsmyrna80]

What mag did you use? Agree that the second looks like a bristle.

 

[ThRoewer]

First looks to me like a nematode
Second is for sure a bristle worm
Third - I don't know.

 

[tannersmith2000]

Thank you all for the replies