What are these?

[Carz]

A friend got these growing on a rock in his sump. Good or bad?

 

[ndrwater]

Looks like sponge. Are they soft? If so, good thing

 

[Carz]

I guess I should mention it is the tubular growing critters. Looks like feather dusters but I am not sure.

 

[Carz]

they are hard

 

[UCF Alum]

vermetid snails with a side of green bubble algae.

 

[VB313]

Are they hard ?kinda sorta looks like vermetid snails

 

[Softhammer]

Bad. I see a crapload of Vermetid snails. And yes, they are tube worm like. Kill at once. They send out mucous nets to feed and irritate corals to death and very rapidly reproduce to plague proportions.

 

[KJ]

Vermetid snail.

 

[Carz]

how do you kill these? Just pluck them off

 

[VB313]

Idk why I second guess myself lol , I use dental tools to remove mine then my emerald crabs seem to be eating them after I break the stalks also they would also help some with your bubble algae in the picture

 

[Mary Carmen]

Bubble algae and vermetid snail. Both are almost impossible to get rid of. I wouldn’t put it on my tank. I actually have vermetid snails and they irritate my corals when I clean the rocks.