Weird worm things?

[Tylerofz]

So i have been finding these weird stringy worm things in my axolotls tabk and they are the same color as his substrate i dont know if its substrate sticking to poop or something i should worry about. Other than these things he appears to be showing no signs of stress.

 

[ellenc]

Are the stringy things moving/alive? What is the substrate?

 

[AxieTails]

I can't quite tell from the picture, but there are two possibilities i know of.
There is a kind of brown algae (harmless in my experience) that can show up in stringy, worm looking shapes.
There are also some worms (forgot their name) that show up when there is uneaten food in the tank, but i haven't seen them stick to some thing like that.