Let's Play "Name That Hitchiker".

OK, picked up some LR last night and after being charged double the price and having to take it back to the store to have it re-weighted it ended up in my tank.

Looks like an excellent place for pods to thrive.... and obviously something else.

Obvious filter feeder if you look just slightly to the left of center in the picture you can see some of it sticking out.

 

wait isnt that a goniopora? (referring to that rock you have there)

 

Might be a barnacle. Looks like it could be algae by the color.

 

Does it go in and out in 2-5 second intervals? I have some barnacles in my tank and it looks similar.

 

Looks like it was probably beautiful when it was alive just from the configuration.

Is it a good / bad / indifferent thing to have?

No it stays out unless you try to touch it then it retracts like a feather duster.

It seems much less shy though as it comes back out almost as soon as you move your finger back.

 

Barnacles arent a bad thing to have in your tank, I like mine, amusing to watch as they feed. Its said that barnacles are hard to get to reproduce in captivity so I doubt they would be a nuicance unless it is pestering a coral.

Could be a type of feather duster. There are some called Sabellidae that dont have hard tubes, such as the Hawaiian Feather duster.
Worm Hitch Hikers
Scroll down to Sabellidae and see if the first 3 pics look similar.

 

Awesome website going to have to bookmark that. It does look similar, but the main distinction I see in watching the behavior is that when it does pull the "feathers" in they close like a clamp kind of "V" shaped and they close like a venus flytrap and then retract in unless the dusters that pull in kind of uniform.

It may be due to the rock that it's in as well limiting how it retracts.

 

Its a barnacle lol The distinct V shape normally gives them away.
YouTube - Barnacles feeding
There are a few different types of barnacles. These stay open when they eat but see if they look similar.