Cardinal Tetra Fish
The Cardinal Tetra looks very similar and is often confused with the Neon Tetra. The Cardinal Tetra will have the red stripe the full length of its body on the lower half, whereas the Neon Tetra will have the red stripe only half way. These tetras make excellent community tank mates and for best results you should keep them in a school (shoal) of 6 or more.
The cardinal tetra prefers water slightly on the acidic side and for best results you'll want to acclimate them very slowly to your tank. Slowly mix in a little water from your tank to the bag they came in over a period of an hour or more. They can be very sensitive to dramatic changes in water chemistry (especially pH). Though these Cardinal Tetras should fare well if properly acclimated, this is not the fish to add to a new aquarium. Make sure that your tank has completed the aquarium nitrogen cycle. Give the Cardinal Tetra a tank with low light levels and lots of aquarium plants.

 
It can be difficult to differentiate the male from the female Cardinal Tetra, but there is speculation that the females are a little bit larger than the male.