I am down to two Apist. borellis in my 55 discus tank. One is definately a male, he has that steel blue coloration and the very long fins. The other I am not sure what sex it is. It is a muddy brown color, its fins are not long, and it is much smaller in size. They are both the same age, it has never showed the bright yellow color of the female, but I wonder if this occurs after it has first spawned? Or is this a submissive male that will never mature as long as there is a dominant male around?