I'd help please...

[mbd521]

I have this funny looking thing on one of my live rock pieces... I really cannot get a good picture of it but i think I cam describe it very well....
Its small and lives in a white hard tube (similar to a feather duster) but instead of the (IMO) pretty upside-down umbrella shape of a feather duster it just has two "tenticles" that hang out of the tube and feel around on the sand and rock. The tenticles are white.

Is this thing safe? It appearance pretty harmless to me ,but so do many other things that probably aren't so harmless...

Again sorry for no pic but I really just couldn't get a good one...

 

[Khemul]

I have a bunch of those. Haven't noticed any issues with them. Pretty sure they are just another type of filter-feeding worm commonly found in aquarium.

Their reach and size depends on the environment. With fish in the tank I find they have an extremely short reach and filter feed (fractions of an inch). No fish in the tank and they stretch out up to a few inches and actually search around for food.

 

[greech]

Spionidae, Chaetopteridae or most likely a Phyllochaetopterus species worm. Harmless filter feeder. The worm itself is way down in that tube and the 2 feelers you see are just feeding tentacles and what the worm uses to build its tube (you'll see them drag sand particles back to the tube sometimes).