Well Dreamer asked for my hardest question, and that was about as hard as I could come up with in the timescale.
Ninjouzata is quite correct, that is indeed a male Xentoca Eiseni, common names include redtail splitfin and orangetail goodeid. If you click on the image to enlarge it, it's easier to see that the anal fin has a notch in it, making it look a little like a child's mitten. The "thumb" part of the mitten is called an andropodium, and performs a similar role to the gonopodium of a poecilid livebearer.
Ninjy, over to you.