i got cultured live rock and i have a piece that have these little tiny feather duster type things popping in and out of the rocks that look somewhat like coral but are definitely not. What could they be?
They're moving? Like little waving hands? If so, it could be barnacles. Try this site: http://www.lionfishlair.com/hitchhiker/hitchhiker.shtml it lists just about every hitchhiker you may ever encounter in your tank(s).
i got cultured live rock and i have a piece that have these little tiny feather duster type things popping in and out of the rocks that look somewhat like coral but are definitely not. What could they be?
It is a U.F.O.
Unidentified Feathery Object )):
It's either a Sabellid or a Serpulid, both filter feeders that are beneficial to your tank! Unless, its aiptasia, which can be a pest.
Sabellid
Serpulid
But if it looks like this.... it's a pest anemone called aiptasia... but they won't go in and out of the rocks like the other two... so probably not it.