Strange worm like growths in sump

Question
Hello Michael,

I recently noticed some strange hair/worm like structures growing all over the walls of my sump.  These structures are anywhere from a quarter inch to a couple of inches long.  They are stationary on the walls of the sump and are in the shape of a worm.

I scraped a couple of them off and their exterior are hard, almost like a calcium build up.  They are white in color and have a brown vein like substance running through them.

I've had this marine FOWLR setup running for approximately 1 year and have not noticed these structures before now.

Any ideas?

Thanks,

-Pete

Answer
Hi Pete,

These indeed are a species of filter feeding worm.  Commonly known as feather dusters.  Feather dusters are highly beneficial to your aquarium as they constantly assist (on a small level) in filtering your water of floating organics.

I have literally thousands of these in my tank.

Kind Regards

Michael