What is this?

[jdmerrit]

I'm new to the hobby and my tank has been set up for 4 weeks with live rock. It is a 46 gallon tank currently with 20 lbs of live rock. Since my tank is obviously still cycling there isn't anything in it. When I came home today I found something unusual in my tank. I can't figure out how to post the picture, but it is about the size of a quarter and look like and dandolion spore. It seems to be attached to my life rock. Any idea what it could be? I purchased the life rock from Old Town Aquarium here in Chicago which has a very good reputation. If it is something how is it surviving since I haven't put any food in there?
Thanks

 

[sharkboy13]

hmm by ur description it could be a multitude of thingd sltho im guessing by wat u say it is aitipsia which is a pest and will sting small fish and inverts and compete w/ coral

 

[jdmerrit]

Should I kill it? If so how? Looks like peppermint shrimp eat it? How did it grow that big in a matter of 8 hours?

 

[fishygurl]

it was proabably hiding in a way like feather dusters can retract.. im not sure just a guess(i didnt grow in 8 hours) if it isnt what i stated above u just probably didnt notice it i see stuff new every once in awhile

 

[jdmerrit]

I'm guessing it's what Shakeboy said. Did it hitch a ride on the LR when I bought it? Peppermint shrimp? Or should I try getting it out a different way?

 

[ophiura]

I would personally say it is more likely a featherduster which is very common at this stage and looks much more like your description. DOn't start killing things until you've searched at pictures of featherdusters, versus Aiptasia.