I've got a 5 gallon tank right now; had it for about 3 weeks (as of June 20, 2013). I originally got it for my toddler son who loves fish, but I've found love for them as well.
In my current tank, I have these little guys: 1 neon tetra, 1 black neon tetra, 1 serpae tetra, and 1 silver tip tetra. It's really neat how even though they're different, all the tetras mostly stick/group together. With them, I also have 1 blue mickey mouse platy, and 1 other platy that I can't remember the name of, but it looks like this: http://www.plantedtank.net/forums/images/fish/785_Platy_Xiphophorus_maculatus.e.jpg . Both platies are female.