A little female of Tripterygion tripteronotus is only five or seven centimeter long.
I've found one more little fry at the top left of the picture, almost in the same pose as the gobby is. The head is out of focus, but it's pop-eyes, finies and a body with a pattern of white dots can be distinguished clearly.
It might be about a centimeter long in size.
I wish I knew it being there, when making a shot.