Fern leaf like creature at night in rocks

[TonyV]

So at night while snooping around with a flash light, I see these creatures mostly in my LR in my sump that resemble a fern leaf flowing in the current. They are clear/white and do not resemble anything like a brittle star or feather duster. They can reach upwards of about 2" in length and are no wider than about 1/16". I've tried grabbing them with tweezers but no luck. They slowly retract when bothered or when lit up with a flash light so taking a pic is impossible. Any idea? Harmless or harmful?

 

[Mel-E-Mel]

Sounds like a fan worm. harmless if it is. does it retract into a calcareous tube?

 

[TonyV]

No tube that I can see of. It's got "leaves" or what not all the way up. The tip is a bit wider than the rest.

 

[DVA]

Copiopods maybe? Are there a lot swimming around or just one or two not moving around?

A photo would be helpful.

Set up a tripod and dial in the camera settings before lights out and then capture that critter on film/byte.

David

 

[Elysia]

Maybe hydroids? There are some that are feather-like in appearance.

 

[TonyV]

So hard to photograph this thing. These creatures are literally the size of a piece of thread floating up from inside the rocks. Many are upwards of 2-3 inches long.

 

[BEASTIEPENDENT]

Maybe some sea pens?

 

[iamwhatiam52]

If it is as fine as the smallest spider web, it may be sessile ctenophores.

 

[eisaiasjr]

Is this what you are talking about???

If it is, you are a lucky guy, they are a detritus eater. They are a very good addition to your tank.

Best Regards,

E

 

[TonyV]

Very well could be the last photo. Any name for these?

 

[eisaiasjr]

Terebellids family... not sure what specific worm it is

 

[BEASTIEPENDENT]

That would be http://www.reeflex.net/tiere/2280_Phyllochaetopterus_sp..htm

 

[Leviathan_XE]

If it is the creature that eisasasjr posted then it's a chaetopterid worm. They're harmeless detritus eaters. I've had one (that I know of) in my tank for years. They use sand to build a burrow and extend their "arms" out sweeping up what they can. But from your desciption earlier it sounded to me as if you had some digitate hydroids, which can be a problem in large numbers as they may sting fish as they swim by. Do a google image search for both to narrow down what it is you really have. HTH.

 

[TonyV]

Leviathan I just did a Google search on digitate hydroids and I think that is what they are. Now on to reading about getting rid of them.

 

[TonyV]

Looks like this from my google searches.

 

[Leviathan_XE]

Yep, that's them alright. Honestly I haven't had luck getting RID of them but they have dropped off to a point where I have to hunt to find one. Like a lot of little critters in our tanks the population will explode then drop back to acceptable levels with proper care. I first noticed one, then a week later there were about seven of them, a month later hundreds. I dropped back on feeding & upped water changes. Slowly most of them died off and my tank was back on the right path.

 

[Elysia]

I tried... Hydroid populations often explode when you feed small particle/suspension foods like baby brine shrimp. Depending on the sensitivity of the animals in your tank, they range from annoying to dangerous.