Yellow clown Gobies laying eggs!

[Duker]

Ok, so my yellow clown gobies have layed their first batch of eggs....YIPPEE!
I was wondering if anyone out there has any idea which one the female would be, one is guarding the eggs/nest ferociously--the larger of the two, and the other one hangs around and "dirty dances" with the bigger one from time to time, but considerably smaller. Now i don't know if the size difference is cuz i've had one longer (started out larger when i introduced the second one) or if the size difference is like alot of other fish dimorphism between the sexes;
eg. like clowns, the female (dominant) is larger than the male (submissive).
Any ideas out there?