We have worms...

[Riptide]

The question is, should I be concerned or not?

They came in on our live rock and even though my tank is still cycling and the live rock is not cured yet they are thriving.

Are these a pest species? They seem very interesting to me and beautiful in their own way. They seem to be spreading though, and fast.

They look like a small feather duster worm but their tubes are white and are parallel to the rock (ie, stuck against it, not out from it) except for the end which seems to curve away from it.

Should I be pleased by the growth I'm seeing here or worried? They look nice enough but I'm concerned they'll take over the tank.

What do you all think?

[Riptide]

OK, these photos should help.

I want to add that these are not worms in that they move around. Their white tubes are attached to the rock. They have an end on them that is just like a feather duster and they look like little flowers when out of their tubes. They are capable of retracting if startled or whatnot.

The white squiggly stuff in the picture is their tubes. I could not get any real closeups bust rest assured - they have a "flower" like end to them just like any normal feather duster.

What the hell are these? They are spreading quick. :) :D

I hope this is a good sign.

[Riptide]

A second photo. The feather duster portion of the worms are barely visible here, but you can start to make out the tentacles (if that's what you call them).

[dethjam316]

i have these guys in my tank too. never noticed a problem from them, so i just assume they're another part of the diversity in the tank, which is usually good. but i'm no SW pro, i only have this one tank in which i'm having my first SW experiment.

[OrionGirl]

There is a real name for them, but I've always called them stony tube worms. They are harmless filter feeders, and seem to go in cycles in my tank. Sometimes they are abundant, then die back, only to come back. The only problem I have with them is those tubes they leave behind--they will grow on your glass, powerheads, etc, so can be a pain to clean up after. As with their larger cousins, the feathery feeders are usually called a crown.

[Riptide]

Cool. Sounds like they are a beneficial organism even if they do end up overpopulating or "blooming" for a while. I don't mind... I'd rather see them get out of control than algae. :)

Maybe my tank is getting close to finished with regard to the intial cycle. I'm going to do a ammonia/nitrite/nitrate test this weekend and hopefully it'll be done so I can put a few snails/crabs in there.

[liquafaction]

I have heard of them clogging powerheads, and filters, but have not had a problem personally. I had a hang on filter that was pretty packed with them, but not enough to stop water flow.