Red-eye Tetra

The Red-eye Tetra is a hardy, adaptable characin native to slow-moving rivers and floodplain habitats across a wide swath of central South America, including the Parana, Paraguay, and lower Amazon basins. Its most distinctive feature is a vivid red band across the upper portion of the iris, contrasting sharply with the otherwise silvery body and giving the species its common name. The body is moderately deep and laterally compressed, colored in bright silver with a faint golden sheen along the back. A bold black vertical bar marks the base of the caudal fin, bordered by narrow white edging that emphasizes the tail's dark marking against the pale body.

• Vivid red band across the upper portion of the iris
• Bright silvery body with a faint golden dorsal sheen
• Bold black vertical bar at the base of the caudal fin
• Narrow white edging bordering the black tail bar
• Moderately deep, laterally compressed body shape
• Deeply forked caudal fin

The striking red iris coloration is the most reliable identifying feature of this species, clearly separating it from similarly silvery Moenkhausia relatives that lack the vivid red eye marking, even though several share a comparable black-and-white tail-base bar.

Red-eye Tetras are native to a broad range of slow-moving rivers, streams, and floodplain lakes across central South America, spanning the Parana, Paraguay, and lower Amazon river basins in countries including Brazil, Bolivia, Paraguay, and Argentina. This wide distribution reflects the species' considerable adaptability to varying water conditions, from clear to turbid, and softly acidic to near-neutral chemistry. They favor open water near vegetated margins, schooling over sandy or silty substrates in both flowing rivers and calmer floodplain habitats. Seasonal flooding across much of their range periodically connects river channels with adjacent floodplain habitats, allowing populations to disperse widely and access additional foraging areas.

Red-eye Tetras are hardy, active schooling fish that move in loose to moderately tight groups through open and mid-water areas, showing more resilience to varying water conditions than many delicate tetra species. They are omnivorous, feeding on small invertebrates, algae, and plant material found throughout their varied river and floodplain habitats. Their adaptability and boldness make them somewhat more assertive than smaller, shyer tetra species, and they compete readily for food in mixed groups. Reproduction follows the typical scatter-spawning characin pattern, with adhesive eggs deposited among vegetation or open substrate and no parental care provided afterward, leaving offspring to disperse and develop independently within the floodplain ecosystem.