X-ray Tetra

The X-ray Tetra is a small, highly translucent characin native to coastal river systems of northern South America, named for its see-through body that reveals the faint outline of internal structures, evoking an X-ray image. It naturally occurs across a range of salinities, from freshwater streams to brackish coastal waters, reflecting an unusually broad tolerance among tetras for varying water chemistry. The body is pale golden to silvery and largely transparent, allowing light to pass through the flanks. Distinctive black, white, and yellow markings on the dorsal and anal fins create a bold three-toned pattern that stands out sharply against the otherwise clear, understated body coloration.

• Highly translucent, pale golden to silvery body
• Internal structures faintly visible through the transparent flanks
• Dorsal fin marked with a bold black spot bordered by white and yellow
• Anal fin bearing a similar black, white, and yellow pattern
• Small, deep-bodied shape relative to many slender tetras
• Forked caudal fin, typically clear or lightly tinted

The distinctive black-white-yellow flag pattern on the dorsal and anal fins is unique among common aquarium tetras and, combined with the body's notable transparency, makes the X-ray Tetra difficult to confuse with any other widely kept species.

X-ray Tetras are native to slow-moving coastal rivers, floodplain lakes, and estuarine tributaries across the Amazon, Orinoco, and Guiana drainages of northern South America. Unusual among tetras, the species tolerates a range of salinities and can be found in both purely freshwater habitats and slightly brackish water near tidal influence closer to the coast. It favors calm, well-vegetated waters with soft, slightly acidic to neutral chemistry, often shoaling in open areas near submerged plants rather than deep cover. This broad habitat tolerance, spanning fresh to brackish conditions, is considered a key adaptation allowing the species to occupy a wider range of coastal lowland environments than most freshwater characins.

X-ray Tetras are peaceful, highly active schooling fish that move constantly in tight to loose groups through open and mid-water areas. They are omnivorous opportunists, feeding on small invertebrates, zooplankton, and organic detritus suspended in the water column. Their tolerance for varying salinity allows populations to shift between freshwater and slightly brackish habitats seasonally as coastal water conditions change with tides and rainfall. Reproduction follows the classic scatter-spawning characin pattern, with adhesive eggs released among fine vegetation and no parental care afterward. Their constant shoaling activity and flashing fin markings make them a conspicuous, easily observed species within mixed-species aquatic communities across their native coastal lowland range.