its not a coral its called an Aptasia , basically a pest anemone . your better off killing it and getting it over with before it spreads (and it will) . Look them up online , theres all kinds of ways to kill them . Heres a site for all kinds of things you'll end up finding in your tank as time goes on .
Xtalreef Its going to amaze you at the things that are going to start growing and just end up crawling around your tank at night . 3 years later and I'm still surprized at some of the things I find .