ID this coral !

hey people, ive had this piece of coral going on a year now its going really well and looks fantastic during the day has it sways back and forth in the current! i love it so much that i went to the fish store to pick up some more to fill in the spots on the sand bed. when i got there i showed them the picture and they were clueless as to what it is so! My question is what type of coral is it?
this one is green with tiny pink mouths and im sure i saw others with different colours when i bought it but no luck on getting more. at night the "fingers" retracted into this purple tubes. so yeah just need to know the name of it
thanks for your time guys!!

 

GSP (Green Star Polyp) some call it a weed, because it grows very fast and will cover anything in it way.

 

thanks for your reply, didn't realize it could grow so quickly ill have to keep an eye on it then and make sure it is controlled!
thanks again!

 

Put some Euphyllia (frogspawn, hammer, torch) around it to keep it in check! Or get a herd of Sexy Shrimp! They'll keep it trimmed down.