Buenos Aires tetra (Hyphessobrycon anisitsi) is a large tetra species characterized by their flat silver bodies, red fins, and black tail spot.
The Buenos Aires tetra will grow up to 3-inches from nose to tail. They are a hardy species, which will thrive in a wide range of temperatures (low 70's to high 80's). These are shoaling fish, and should be kept in a minimum school of 3. Due to their size, they should be kept in at least a 20 gallon for a small school. Larger schools of 6+ need at least 30 gallons.
These fish are semi-aggressive and have a tendency to chase smaller tankmates. They should be kept with other semi-aggressive fish species. They tend to nip the fins of other animals such as angelfish if the shoal is too small.
Photo by Nick Sc. - Own work., CC BY-SA 3.0, for Wikipedia (English).