ID these fast swimmers please!

[Kjames]

First time noticing these. Several came out after some pellet food floating on the surface. At first I thought they were detritus blowing around until one swam to the surface then back down to the bottom. Reminds me of mosquito larvae. About 1/8” long with rapidly moving fins/legs(??) I’ll try to link a video.

 

[sfin52]

Looks like bristle worms

 

[Kjames]

Duplicate post

 

[Kjames]

This should be a little easier to view.

 

[vetteguy53081]

Appears to be a dorvillidae worm which does swim in tank but man that is some fast movement

 

[Maritimer]

A lot of the polychaete (bristleworms, dorvilliid worms and many, many others) have what's called an "Epitoke" reproductive phase. They can seriously _move_ through the water column, and help to distribute the next generation of worms across a pretty wide area.

(Depending on the species, they also help to feed the local fish population!)

~B.