Hemigrammus bleheri, the Rummynose Tetra

Hemigrammus bleheri (Rummynose Tetra). Randy Carey's 1993 article, "The Three Species of Rummy-Nose Tetra" distinguishes among the three species that might be mistaken for one another. If you're interested in these tetras with a reputation for being delicate, that's the first place to look. If you're looking for a consistently schooling tetra, the Rummynoses fill the bill. Conversely, don't keep them in groups of fewer than six.
 
Hemigrammus bleheri at FishBase.  Rummy-nose tetras at Wikipedia.