What is this?

[footballdude2k3]

Not my picture, but got a big chunk of this, just curious on what it is, thanks!

http://i238.photobucket.com/albums/ff210/footballdude2k3/ScreenShot2013-07-11at12553PM_zpsef4b2f00.png (http://s238.photobucket.com/user/footballdude2k3/media/ScreenShot2013-07-11at12553PM_zpsef4b2f00.png.html)

[Arkayology]

I would say A. validia or A. nana, though I am known to be wrong :D

[Frick]

+1 I am leaning more towards Acropora nana.
http://coral.aims.gov.au/factsheet.jsp?speciesCode=0050