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Hey anybody know what this guy is? He's pretty small, just a couple cm is the length you can see and maybe a mm or two in diameter. He hasn't seemed to harm anything, just eats around on the sand near his hole in the rock.

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Critical Fertilator: The Micromanager of Macronutrients

I saw him last night after a water change while I was taking pics(which I'll post some up later tonight). Here's another shot of him trying to grab the sand:



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Critical Fertilator: The Micromanager of Macronutrients

You will have your work cut out with that critter.

It looks to my (untrained in this respect) eye as if you have a polychaete worm of some kind. Which could be good news if it's a harmless detritivore, but if it's one of the Fireworms, it could be BAD news.

Some links are apposite here:

Bristle Worms And The Pest Control Thereof

More Bristle Worm Control

Reefkeeping.com page on Polychaete Worms (on this page scroll down to the 'Mobile Worms' section)

This is a job for a trained professional strictly speaking, as the level of expertise even amongst seasoned salties with respect to polychaete worms is likely to be low, other than the familiar Feather Dusters et al. Trouble is, some Families of mobile polychaete worm are difficult even for the experts to identify, and for precise work they resort to electron microsocpy, which is almost certainly WAY beyond your reach unless you're working in that environment ...

However, there are quite a few mobile polychaete worms that will assume pest status in your aquarium rapidly, so it is a good idea to have this guy checked out by a professional in the field - the pest worms will grow to amazing sizes at lightning speed, and once they grow big, they'll wreak havoc.

If your worm checks out as being a harmless detritivore, on the other hand, then you can keep him as part of your clean up crew. Watch closely for any sign that this worm takes an interest in things other than food particles in the substrate - particularly if you have anemones in there. If the worm starts snacking on anemone tentacles (and several Fire Worms do this) then determined and resolute action to deal with the creature is called for!

Be advised that some Fire Worms can deliver a sting that is painful to humans. So if you DO have a Fire Worm, you could be in for some fun and games removing it ...


Panda Catfish fan and keeper/breeder since Christmas 2002

Nah, it's not a bristle worm, or fire worm. It's smooth and cylindrical. It doesn't have bristles. It's head seems to suck up into it's body when it retracts, but doesn't have a hard outer shell or whatever. I've creeped around the tank at night with a red light, and I've never seen it about. I think it actually only comes out during the day, which seems to be odd for worms.

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Critical Fertilator: The Micromanager of Macronutrients

I think it looks like some type of peanut worm(Sipunculids). I have a plain pink one in my tank but I've seen pics of black striped ones kind of like that.

Ah, something new for me to add to my list of inverts to learn about!

Reefkeeping.com came up trumps with an article on Sipunculid worms that may prove helpful.

As to identifying this creature, that is, from what I can gather, very definitely a job for an expert, and will almost certainly require dissection, if your worm is indeed a Sipunculid. The good news is that if it IS a Sipunculid, it's a harmless detritivore.


Panda Catfish fan and keeper/breeder since Christmas 2002

Great detrivores. I disagree with the article on them not being very exciting or active. Sometimes mine is more active than my shrimps and goby. It's always extending out and scraping through the sand. It lives in an overhang of rock and there's always a little pile of detritus under it that it's been picking through. Very quick to dissapear though if disturbed. I bet they'd make a very easy meal for any carnivorous fish or shrimp. Unfortunately they don't seem to handle shipping great. There were also 2 damaged worms that didn't survive.