Bristleworm ID???

[flyinhippie]

Fish in quarantine 1 month recovering nicely from fin rot. Daily water changes 20-50%. All dietrus removed from floor each time. Fish has a habit of pooping immediately after medicating / water change.

Did not see him poop this particular time but after close examination realized that these images, 5 min after water change, are some type of bristleworm. They are black with white bristles.

I wouldn't think these type of worms from the looks would be internal. I'm using a seasoned sponge in a hang on filter. They could have come from there, but I'm not so sure.

Any thoughts?

 

[Hemmdog]

Strange, following along.

 

[flyinhippie]

Update: confirmed that the bristle worms did not come from the fish. They were living in the sponge of the hang on back filter.
Did a paraguard dip on the sponge and it was infested.
Will throw it out and start the biological filter over.
Still looking for an ID on the type of worm.