they are between 6-7". Actually, I would say the male is 5.5" and the female is 6.5", even though they were the same size when we got them. She (we think its a she) has grown SO MUCH faster than the other one.
I just found it interesting how they have a green sheen- and they are much bigger than ones I've seen which have already lost their external gills, but ours still have them.
and the coloring is different... from the other ones I've seen.
The top pic is the male, the female is quite a bit larger.