The X-ray fish is a real, fascinating creature, captivating people with its unique, see-through body. Scientifically known as the X-ray Tetra (Pristella maxillaris), this small freshwater species belongs to the Characidae family. It typically reaches a maximum length of about two inches. Its common name refers directly to its most distinguishing characteristic: a largely transparent body.
Why the Fish Appears Translucent
The remarkable transparency of the X-ray Tetra is a result of a biological adaptation. Unlike many fish that possess dense layers of pigmented cells in their skin and muscle tissue, the X-ray Tetra has only a faint, silvery-yellowish sheen. The near-absence of these pigments allows light to pass through the body largely unimpeded.
The fish’s skeletal structure and internal organs remain visible through this translucent layer of skin and muscle. One notable structure that becomes especially prominent is the Weberian apparatus, a bony formation connecting the swim bladder to the inner ear. This visible internal anatomy contributes to the illusion of seeing through the fish. This natural camouflage helps the small fish blend into its environment and avoid detection by predators.
Natural Range and Ecosystem
The X-ray Tetra originates from the tropical freshwaters of South America, specifically across the Amazon and Orinoco river basins. Its natural range extends through the coastal regions of Venezuela, Guyana, Suriname, French Guiana, and northern Brazil. This species is highly adaptable, inhabiting environments that experience seasonal fluctuations in water conditions.
During the dry season, the fish typically resides in clearwater streams and tributaries, foraging for small invertebrates. The tetras migrate into flooded areas, such as savannahs and coastal swamps, during the rainy season. The water in these habitats is often soft and slightly acidic due to the decomposition of organic matter.
Care Requirements in Aquariums
The X-ray Tetra is a peaceful fish, making it an excellent addition to a community aquarium setting. Because they are schooling fish, they must be kept in groups of at least six individuals. A minimum tank size of 15 gallons is recommended for a small school.
They thrive best when the environment mimics their natural South American habitat. The ideal water temperature should be maintained between 72 and 82 degrees Fahrenheit, and the pH should be slightly acidic to neutral, ranging from 6.0 to 7.5. Regular partial water changes are necessary to keep nitrate levels low.
As omnivores, X-ray Tetras require a varied diet. A foundational diet of high-quality flake or micro-pellet food should be supplemented with protein-rich treats. Offering frozen or live foods, such as daphnia, brine shrimp, or bloodworms, ensures they receive all necessary nutrients. A varied feeding schedule promotes active foraging behavior and contributes to their longevity, which can be up to five years.