What are these worms?

[Myrtle]

I wasn't sure where to put this, but can anyone ID these? They're in an old tub outside that I use for daphnia etc, but also works as a bit of a wildlife refuge. I spotted them and wondered if they could be fed to the fish occasionally? I assume they're some kind of detritus worm?

 

[Conort2]

I wasn't sure where to put this, but can anyone ID these? They're in an old tub outside that I use for daphnia etc, but also works as a bit of a wildlife refuge. I spotted them and wondered if they could be fed to the fish occasionally? I assume they're some kind of detritus worm?

They look exactly like blackworms which are great fish food. I’m assuming there are probably a lot of species which look very similar.