This is a true rainbow goni.  We have several different kinds and this one gets some amazing colors and will behave differently in different light intensities.  In higher light the tentacles stay fairly short.  However in dinner lighting they can get very long, just as long as other long tentacles gonis.  
 
Frags will be 3/4"-1".  Pics are for representation of the coral only.  Frags of the coral are very similar but not exactly as seen in the photo.  Please visit our WYSISYG section if you want to purchase exactly pictured corals.