I Found this GROWING in my tank? What is IT?

[superior]

Hi everybody, recently I got a tank from a friend of mine it is a 180gallon with a 50 gallon sump. I did not run the Halite 250watt 20k bulbs for awhile because I didn't think there was any corals in my tank.

I have added 5 small corals and for about 3-4 weeks I have been running the High Pressure Halite bulbs for 7 hours a day and all of the sudden I saw this growing in the tank.

It shows a very slight movement in the water. it is about the size of a half dollar, and you can see the white tentacles (where it is attached to the live rock)

Can you identify what type of coral this is? how big will it grow? (I Circled the item and used an arrow to show where the white tentacles attached to the rock are, I have uploaded 2 different pictures (1) with a flash on my camera and (1) without using a flash)

 

[yote]

Its hard to really tell.But it looks like it could be a leather coral.
And they can get pretty big(as with any coral that we dont kill).

 

[superior]

Its hard to really tell.But it looks like it could be a leather coral.
And they can get pretty big(as with any coral that we dont kill).

Thanks, I know that its hard to tell from the pictures. If anybody else has some ideas please post them.

 

[dustin_P74]

some kind of sponge possibly?

 

[SSalty]

The first impression that I got is a Leather Coral or maybe a Cabage Coral.

 

[messiah023]

Could be two different things.....
There are white tentacles there behind the brown caps.
Could be an aiptasia head or possibly a corralimorph?

Any way to get a better close pic?

 

[daugherty]

my guess is a gabbage coral i had one the looked just like that a couple monyhs ago