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Mystery growth near base of coral

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The Lost Tapes

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Nov 24, 2021
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Can someone help me identify what this thing is, its hard and feels like a shell of something, i have seen it grow over several months and am wondering what it is, its obviously some type of living animal since I've seen it grow in size, but what exactly is it? I can post more images if needed
More pictures please.

Could be a barnacle. Have a look at it after the lights have been off for an hour or so and see if it has a clear hand/ claw like thing coming out the top.
I havent ever seen a claw when I've looked at the tank at night. Also all the pictures of barnacles I've seen have different shapes and colors but not like this, so I dont think it is one, given they are filter feeders wouldn't they need a lot of food? Compared to a coral or sponge which i do have
Pic is still too blurry to make out. If you hadn't said it was hard it looks vaguely like some sponges/tunicates in terms of globby shape but I'm guessing that's just an artifact of the blur then. Is you've seen a "claw," does it move rapidly? If it whips in and out, then barnacle. If it just kind fo sits there or only rarely goes in and out, there are filter feeding worms that have similar filter feeding mechanisms and produce messier looking shells than barnacles.

iven they are filter feeders wouldn't they need a lot of food? Compared to a coral or sponge which i do have

Yes, but if it's only one there may be enough in there, for now anyway. Barnacles are hard to keep long term but short term survival and growth of small ones is pretty common. However, various marine worms and things like vermedid snails are more common as long-term survivors in small tanks.
Its in a 40 gallon tank, i do feed reef roids daily so that may keep a barnacle alive given my sponge and corals are doing well. But this thing came in with the coral and has just been doing its own thing there for months, what kind of images would be best to identify it? Top down?
Maybe a short 1 minute video of it. You can upload videos to YouTube, then copy & paste the link here.
If you use a mobile phone to film it, hold the phone horizontally (landscape mode) so the footage fills the entire screen.
what kind of images would be best to identify it? Top down?
It's the blur and oversaturation that's making it hard to figure out I think, not so much the angle. Can't tell what shape it is really or where the opening is if there is one (or more than one). A short video clip like colin sugested might get around that if it's high enough res; sometimes shapes are visually easier to pick up on from a slightly moving image than from a static one even if each individual frame isn't pristine.

It had a tentacle or something out but it retracted so quickly i couldn't see what it was
could it be the base of another coral seeded onto that disk??? ,looks like there are growth rings on the base???
Well it has grown since i bought the coral, which has been there a very long time so it was a lot smaller originally.
So I saw that it had some tentacle out and when light was shown it retracted, could also be a worm too, but its not a barnacle since it didnt look like an arthropod
The latest pictures are much better :)

It's not a barnacle.

It appears to be a type of tube worm. I don't know what type but Donya might. Otherwise send the pictures to a museum or biology lab and see if they can identify it. It should be harmless and a real curiosity.
Thank you, this is the most bizarre hitchhiker i have ever seen but its pretty interesting.

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