Melanotaenia praecox, or Neon Rainbow.  Amazingly, this fish is relatively new to the aquarium hobby.  While it was discovered in 1920, it was not collected and propagated in captivity until 1992.  Neon Rainbows are native to New Guinea.  They have been found in the Mamberamo River system in northern Irian Jaya.  Their natural habitat is swift flowing jungle streams, usually near surface vegetation, submerged logs, or branches.  There is an excellent reference for this fish on the web, here. These fish are perfect community tank and planted tank fish in that they do not bother their tank mates or eat the plants.  Also, they do not hide, and are nearly always visible.  They tend to prefer swimming near the surface of the tank in schools.  Females are nicely colored like their male counterparts, but tend to have slightly more yellow tone to their fins. The male fish has brighter red coloration to his fins.  Neon Rainbows grow up to 2 inches in length.  They prefer temperatures between 75 and 80 degrees Fahrenheit.   These fish eagerly eat dry food, brine shrimp, and blood worms.