The fish is Poeciliocharax weitzmanni. It is a small tetra from South America, namely Brazil and Colombia. They are very shy and reclusive, and live solitary lives. Males will establish small territories and can be quite feisty toward their tank mates. They require live foods to survive. This fish is rarely imported because it is not that feasible to collect such a small fish in large numbers that would probably need to be caught one or two at a time. You may find these fish however as contaminents in shipments of wild Cardinal Tetras or Paracheirodon simulans (Green neon tetras). This is actually where I got my first group of these great fish. I make it a point to thoroughly peruse tanks of freshly imported wild SA tetras for jewels like this. Hope this helps.
It's a beautiful fish. I used to have ~14 in a 65 gallon tank and have alas sold them. They are very reclusive as aaron says, and I believe the japanese use caves to spawn them. However, they do get fairly large. Mine grew to about 2.5 inches, and they were fed frozen bloodworms, frozen mysis, and even pellets for a time. The males were beautiful while displaying. Most lived for 3 years before I sold them. I haven't seen them since.