What the heck is this on hammer coral?

[moneyman]

I've noticed this thing for a bit and didn't do anything because I wasn't sure what it was but it has been getting larger, and I have no idea how bad it is. When I shine a light on it I think I see a critter or something maybe move inside it, but idk. It is like a hard shell for something. Please help me identify and fix this. (The hammer is closed Becuase this is at night btw)

 

[shcrimps]

fan worm? of sorts maybe
@ISpeakForTheSeas can probably help

 

[moneyman]

fan worm? of sorts maybe
@ISpeakForTheSeas can probably help

Is it bad?

 

[ISpeakForTheSeas]

Large vermetid snail of some variety- the large ones seem to be pretty harmless (they don't seem to reproduce/spread at all or irritate corals from the ones I recall offhand), so if it hasn't caused problems by this point, it shouldn't cause any going forward.

You could keep it or remove it as you please.

 

[shcrimps]

Large vermetid snail of some variety- the large ones seem to be pretty harmless (they don't seem to reproduce/spread at all or irritate corals from the ones I recall offhand), so if it hasn't caused problems by this point, it shouldn't cause any going forward.

You could keep it or remove it as you please.

had no clue that was a thing
the ‘skeleton’ reminded me of some larger fan worms, i should probably read up on stuff more
i always find out new stuff from you

 

[ISpeakForTheSeas]

had no clue that was a thing
the ‘skeleton’ reminded me of some larger fan worms, i should probably read up on stuff more
i always find out new stuff from you

Haha, happy to help - yeah, vermetid snails and some feather dusters' tubes (most commonly in the hobby, Serpulid worms) are both calcium carbonate and can look very similar.

A lot of the time you can tell them apart sort of instinctively (in this case, the pinkish color and the dark lines segmenting the width of the tube cued me in), but other times you may need to rely on seeing either a mucus web or feather crown (if the tube is inhabited) or if the inside of the tube is shiny (if it's shiny, that's nacre from a snail, so it's a vermetid tube; a dull/matte interior would mean a feather duster tube).

 

[DanyL]

@ISpeakForTheSeas pretty much covered it all here, and he’s correct - these are a large variety of Vermetid snails, and they’re harmless.

They can however spread when fed heavily and can be an eye sore for some people, in than case removing them is an option and can easily be done using bone cutters, or a knife/screwdriver.

 

[JayM]

I just superglued one shut on my hammer last week. It had been there for a while with no ill effects, but it seemed to have grown closer to the flesh band and appeared to be irritating the coral.