Nice!
They'd make great posters
The first picture of the couple where they look away from each other is really family-like. If there was slightly more room under the fish, it would have been my favorite!
The composition of the 3rd is my favorite with the fry going towards their... Father?
I guess that the only lighting you used was a flash, which was put on top of the water, pointing downwards. The white bottom of the tank also gives a nice diffuse illumination to the fish!
How did you manage to get a black background? Do you paint your tanks in black?
And finally... You don't see any reflection of the fish in the background glass?
All this being said, thanks a lot for sharing these beautiful photos!
PS: next time, could you try to show us the overall setup? (a simple picture of the tank from far away with the camera, flash etc)
Thanks again!