Friend or foe? Hard tubes with small blackish worms

[WrasseMan89]

A local reefer broke down his tank and hooked me up with some nice live rock. He said he had no pests and it was aptasia free. I pick up a piece and it has small hardened tube's that break off fairly easily and one I broke off had a small critter in it (blackish looking worm thing). So I thought I would ask and see if anyone knew if these were good or bad.

 

[buttonreefer]

Looks like you’ve got vermetid snails. I would remove them because they will continue to multiply and build up their tubes to grow. They can eventually grow on corals and suffocate them to death and cast out their mucus webs. You can glue their tube shut or completely remove them (which I definitely recommend) using an ice pick or bone cutters. Make sure you get the creature inside the tube out, not just the tube- they get all the way inside like a turtle.

 

[ISpeakForTheSeas]

Most of those tubes look like feather duster worm tubes to me, but some may be vermetid snail tubes as well.

Feather dusters send out a little feeding crown that looks like a circle of little feathers - they're harmless and neat.

Vermetid snails send out a mucus net to catch food to eat, and these may sometimes irritate corals - it's generally recommended to get rid of vermetids, but they aren't always harmful.

 

[buttonreefer]

You’re right, now that I think about it, they could just be some feather dusters. I feel silly not even thinking feather dusters. Not harmful, actually pick up stuff from the water column. Kinda cool. Yeah, I do agree those are feather dusters now. If they are, I’d only remove them if you don’t like the look. They also multiply really quickly. Note: he did say he thought there were no pests, but usually the feather dusters that are out of the tube are orange, not black. I guess vermetids killing corals can be a bit of a stretch, but it did happen for me once in recovery of a coral. I’d still remove it if it was a vermetid.