Hyphessobrycon serpae, or Serpae Tetra. The Serpae tetra is a well known and often kept hearty community tank fish.  They are also excellent planted tank fish.  The fish shown in the image to the left are hybrids.  See this link to search for a description and picture of a non-hybridized Serpae.  The Hyphessobrycon genus is distributed over all of South America, except possibly the very far south on this continent.  There natural habitats are still and flowing waters.  Generally, they prefer softer, more acidic water, and are very hearty.  They prefer temperatures of between 72 and 79 degrees Fahrenheit.  They will eat dried food as well as brine shrimp and blood worms.  These are gregarious fish.  However, when first introduced into a tank, they may be shy for a few days.  Soon, they will make themselves quite visible, usually near the front and bottom of the tank.  The hybrid versions are quite a bit more attractive than their earlier cousins, and make an excellent addition to a planted tank.