Where do Detritus worms come from?

[NStalgia]

I'm wondering if these worms can just appear in new aquariums. I'm trying to culture daphnia and one batch died, there's still a couple small ones there but then I noticed these guys wriggling around. Not exactly sure where I got them from and I'm considering if I should throw them away cause they may infect my new tanks. On the other hand I'm thinking if I could use them to feed my betta fry.

 

[NStalgia]

I think this might be related
https://www.aquariacentral.com/forums/threads/infusoria-culture-with-worms.53226/
The water I used for that container came from infusoria that I was trying to culture. Does it turn into that?
Also something related although not any helpful answers:
https://www.reddit.com/r/Aquariums/comments/nm49dt/help_what_is_this_worms_in_my_little_daphnia/

 

[Aiken Drum]

Detritus worms can't spontaneously appear. They have to be somehow introduced. They will come on either with fish or plants, maybe a piece of driftwood or possibly in your substrate.

You wont normally see them, but they can reproduce in huge numbers if you are overfeeding in an already infected tank.

 

[NStalgia]

I see thanks. I've only been putting yeast in that container and I think a dead java moss.

I think this might be the cause
https://www.aquariacentral.com/forums/threads/infusoria-culture-with-worms.53226/
Can it have come from a batch of old infusoria? I left it for a couple weeks and used the water for my daphnia culture.

 

[NStalgia]

I just realized I had a bottle of that infusoria i used left. So I looked at it and yea, seems like that's where it came from. Interesting, so detritus can form from dead plants if left for a long time.