Please help identify?

[Layll318]

Noticed a couple of these growing on some of our live rock. We're new to this, so not real sure what much of anything is, but they're teeny and pretty, and I'd like to keep them if they're harmless! They suck into themselves for a while sometimes, and I'm not sure if they're a coral, or an anemone, or an algae or whatever else. Tia!

 

[Daltonbilecki]

Looks like a cluster duster or feather duster. Harmless if it is one.

 

[Layll318]

Thank you! There appear to be only two of them right now, one a bit bigger than the other. Should I expect to see more pop up? And what type of critter is it? A worm? Thanks again for your help!!

 

[Ron Reefman]

If you see more, good for you and the tank.

They are a worm and they live in the small tube they build themselves. They are filter feeders so they help keep the water clean. Google feather duster and learn all you want to know.