WHAT IS THAT???

[Stin999]

Should I be concerned lol - What is this creature in my rocks?

 

[1112-425XL]

I'm concerned and it's not in My tank!

Following...

 

[DED65]

That is weird.
@ISpeakForTheSeas

 

[SALTWATER FISH HIPPIE]

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[VSVP bet]

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pic for reference, notice the split 'mouth'

 

[ISpeakForTheSeas]

Should I be concerned lol - What is this creature in my rocks?

That's a female Bonelliid Spoon Worm/Echiuran - most spoon worms are harmless detritivores (good CUC), but a few (likely including yours) have a toxin (Bonellin) on their proboscis (the forked "mouth" mentioned above) and/or skin; these eat things like small pods that succumb to the toxin when crawling on/over the proboscis.

These would probably be fine to keep in the tank as long as you think your critters are smart enough not to touch the proboscis, but it may carry some risk (especially for smaller critters, and especially if your female has one or more males - which are tiny - living with it so that it could reproduce):

be aware that it is toxic (the toxin is called Bonellin, and I’m not sure about it’s effects on people), and please handle it with care and a good pair of gloves.

If you decide to keep it, I'd probably suggest running carbon and doing regular water changes to be safe.

 

[Stin999]

That's a female Bonelliid Spoon Worm/Echiuran - most spoon worms are harmless detritivores (good CUC), but a few (likely including yours) have a toxin (Bonellin) on their proboscis (the forked "mouth" mentioned above) and/or skin; these eat things like small pods that succumb to the toxin when crawling on/over the proboscis.

These would probably be fine to keep in the tank as long as you think your critters are smart enough not to touch the proboscis, but it may carry some risk (especially for smaller critters, and especially if your female has one or more males - which are tiny - living with it so that it could reproduce):

If you decide to keep it, I'd probably suggest running carbon and doing regular water changes to be safe.

Interesting!

How can you tell that it might be a female?

Any clue if the toxin is powerful enough to hurt a fish?

I'm okay with the risk to small inverts, but I wouldn't want the loss of a fish.

This particular rock has been in the tank for over a month and a half - no casualties as of yet.

Thanks - Austin

 

[ISpeakForTheSeas]

How can you tell that it might be a female?

Any clue if the toxin is powerful enough to hurt a fish?

Bonelliid spoon worms exhibit extreme sexual dimorphism - the females are large while the males are extremely tiny and often/always live literally inside the female. So, by seeing the worm's regular-sized proboscis extended, you can tell it's female (no idea if it has a male with it or not though).

Unfortunately no idea how harmful the toxin is - as a general rule, the physically greener the worm, the more toxic I would expect it to be, but I don't know how much of the toxin it would take to harm a small fish.