Is this a pest?

[Christopher1492]

Hi. Looooong time lurker trying to decide what system I want to build.

I’m looking at some reselling posts elsewhere and can’t help to think this is some type of pest or???? Can anyone ID the white worm-like things in the attached photo or at least offer an idea.I know the photo quality is poor but this is all the poster offered inside the cabinet.

I realize the filtration system is junk and likely indicates the system hasn’t been cared for but the livestock is really what interests me and the display tank looks pristine.

Thanks for any help!

 

[WheatToast]

Looks like tube/fan/feather duster worms. Harmless filter-feeders. Some cryptic sponges (which are also usually harmless) look similar, but their “tubes” merge with one another.

Tube worms:

Sponge:

 

[Christopher1492]

Thanks for your time and insight. Appreciate it