Blackworms or Microfex?

[divemaster99]

A few months ago I started finding small quantities of these guys in my 75g Catfish tank. Since then, they've multiplied and leveled out to the point that there's thousands of them. I've fed this tank blackworms before, at least a year ago, and while these looked similar, they seemed to small to be blackworms to be. So, I finally brought a sample with me today and looked at them under a microscope. Wasn't easy to get pictures but below is what I have. Look a bit like microfex to me but I'm still leaning towards blackworms, or maybe it's something else entirely. Thoughts?
-Sean

 

[Jackson]

Look like dero worms / micro fex

If they bunch up into balls they're dero worms

Great live food

You finding them in your filter media? Like old floss left in a bucket and they surface?

If they're black worms you'll see them sticking up for the substrate like blades of grass
They don't usually reproduce well in a typical aquarium set up