Buenos Aires Tetra Identification Guide
Practical field marks for spotting the silvery, red-finned Buenos Aires tetra with its bold black tail spot.
Read the full Buenos Aires Tetra encyclopedia entry →
Key identification features
- Elongated, laterally compressed silvery body reaching about 3 inches (7.5 cm)
- Bold black diamond-shaped spot at the base of the caudal fin
- Orange-red anal, pelvic, and caudal fins; dorsal fin often edged in black
- Small adipose fin between the dorsal and tail fins
- Faint dark shoulder patch behind the gill cover, much less distinct than the tail spot
- Fairly deep, streamlined body compared with many smaller tetra species
Common look-alikes
- Serpae tetra: similar red fins but a rounder body and a prominent black shoulder blotch instead of a black tail-base spot.
- Flame tetra: smaller overall, redder-toned body, and it lacks the Buenos Aires tetra's sharply defined caudal spot.
- Redhook silver dollar: much larger, deeper-bodied disc shape versus the Buenos Aires tetra's slender, torpedo-like profile.
Where you'll see one
Native to slow rivers, streams, and lake margins of the Río de la Plata basin in Argentina, Uruguay, and southern Brazil, this hardy schooling species favors cooler, vegetated subtropical waters, tolerates a wide temperature range, and often swims in loose, active groups near open water.
Frequently asked questions
How can I tell a Buenos Aires tetra from a serpae tetra?
Look at the shoulder area: serpae tetras show a rounded black shoulder blotch, while Buenos Aires tetras have a distinct black spot near the tail base instead.
What is the easiest visual cue for spotting this species in a group?
Watch for silvery, torpedo-shaped fish with orange-red fins and a sharp black diamond mark right where the tail fin begins.