whats this stuff in my rock? ID please!!

If I tap the glass it sucks in a little, it glows orange under light like some corals. Some one from a fish store told me it was a sponge, on another fish store the guy told me it was an unopen zoa. i have search the web and found nothing.

 

Can't help without pics.

 

Welcome to 3reef.

Even a bad image helps a little (shhhh do not let anyone know I posted that). Sponges typically show no physical movement you can detect, therefore I am leaning towards a polyp of some sort.

 

google tunicates

 

Yup, colonial types.

 

are they good?

 

Yes, just harmless filter-feeders. Just like a lot of hitch hiker sponges, they may thrive for a while in newer systems; however, they tend to disappear as the tank matures as most of us strive to keep our tanks too clean for them.

 

Thanks to all

 

i believe these polyps
http://www.3reef.com/forums/id/polyp-but-not-sure-what-type-145843.html
are one in the same.
but the type not sure.

 

Very cool, a Botryllus sp.
Botryllus
Star ascidian videos, photos and facts - Botryllus schlosseri - ARKive