Moenkhausia sanctae filomenae, or Red-eyed Tetra. Guyana and the upper Amazon is this fish's natural habitat. They prefer a tank temperature between 71 and 79 degrees Fahrenheit.  This variety does not get bigger than about 7 cm.

I have had fish pictured, no kidding, for over five years now. He is such a small thing, that I would not have expected him to be so long-lived.  Nevertheless, I believe that this is the oldest fish in my tank.  He has lived to his current ripe old age even though  several years back I have had terrible bouts of Ick and one mysterious bacterial epidemic run through my tank. Perhaps he is so durable because he is always hiding from any excitement!  It never fails: this fish is always in the shadows, unless he senses there is food coming.  His stealthy nature has made this fish very difficult to photograph. Finally though, after several tries, I succeeded in sneaking up and snapping this rather poor photo of the senior citizen in my tank.

Red-eyed tetras are extremely easy to keep.  They will eat just about anything they are offered.     A close cousin and similar looking fish known as Moenkhausia oligoepsis can get larger than M. sanctae filomenae by about 5 cm (to a maximum size of 12 cm).  Both types of red-eyed tetras are best kept in schools.  They are very social, peaceful fish.  Mine has always been withdrawn, possibly because for most of his life, he has not had his own kind to school with.  (I never replaced the ones that died before him.)