What is this nasty this??

[Reef_Geek]

I could probably tell you if I had it and a dissecting scope. short of that... no telling what it is.

if you're worried, just scrape it off and toss it. there's a good probability that it is harmless though, just like the variety of surprises that comes in with live rock.

[nerdz]

Probably some kind of tunicate, or sea squirt? Crazy!!!

[Snappy]

Originally Posted by nerdz

Probably some kind of tunicate, or sea squirt? Crazy!!!

plus 1
They are just a filter feeder and good for the system.

[jason604]

It opened up now in my tank. I believe it is a sea squirt. Should I destroy or keep it lol.

[Reef_Geek]

yeah, the two siphons is the classic morphology of a sea squirt. One is the in-siphon and the other is the out-siphon.

It's a harmless filter feeder.

[Coral Hoarder]

ceep it !!! or give it to me for my tank lol