Zoa or??

[St.Pete_Reefer]

Found these growing hard to get a good picture. Inside the middle of them is a green. Long hair style tentacles on outside rim and the rest of the color is brown.

Beside the mushroom middle of picture

Side view next to mushroom

 

[650-IS350]

potential bottom polyps.

http://waterworld.pk/images/soft coral/180010-Button Polyp - Large Brown -Zoanthus palythoa sp..jpg

 

[St.Pete_Reefer]

potential bottom polyps.

http://waterworld.pk/images/soft coral/180010-Button Polyp - Large Brown -Zoanthus palythoa sp..jpg

After looking up that name I think thats exactly what they are.

Info I found:

overview
The Protopalythoa Button Polyp Corals, also referred to as Moon Polyps, Encrusting Anemones, or Sea Mats, are generally brown or tan in color, but may also be green and fluoresce under actinic lighting. They are a colonial animal with multiple individual polyps attached to a piece of live rock or coral rubble.
They are very easy to maintain in the reef aquarium. Their polyps have the ability to sting other animals and are semi-aggressive, therefore, they need to have space between their colony and any neighbors. They also grow rapidly and will crowd out their neighbors including any sessile life. They require a medium light level combined with a medium to strong water movement within the aquarium. They will reproduce easily in the reef aquarium by budding (splitting off a portion of their base or mouth), which will increase the size of their colony. For continued good health, they will also require the addition of iodine and other trace elements to the water.

The symbiotic algae zooxanthellae hosted within their bodies provides the majority of their nutritional requirements through photosynthesis. They benefit from weekly feedings of micro-plankton or brine shrimp which should be fed to each individual of the colony.

 

[St.Pete_Reefer]

I will have to keep an eye on them with being semi aggressive.

 

[650-IS350]

They're invasive growers IMO.

 

[St.Pete_Reefer]

So basically get that rock gone? lol

 

[650-IS350]

You can chip the piece off the larger rock and have that frag grow by itself on it's own island and still enjoy that coral without it growing all over your major rock work.