It is a Duncan, but I've never seen one all white like that. Mine are blue and green, I have had others that had pink too, but never white. Also, in the full tank shot it looks like the duncans might be on the right side, but not sure all those on top are duncans. Never seen a colony that big if they are.
BTW, I have a blue Duncan small colony for sale if you want to take a look at the colors on mine.