Whats this...

[Fishfeet62]

Hi, I've got a question, I'm noticing these things growing on my rocks.. they are spike looking things with a white looking thread that comes out of them at times, are they good or bad ?
I will say after switching to saltwater I'm finding new things everyday...

 

[Reeferdood]

Looks like spionid worms, harmless filter feeders.
Welcome to the forums!

 

[Bryson.bobby]

Vermited snails, can often irritate corals