The X-Ray Fish (Pristella maxillaris) is a small schooling fish native to the Amazon basin in South America. These fish are named for their transparent skin that allows you to see their internal organs and skeleton. They are popular in the aquarium trade and can be found in many pet stores.
Also known as the Golden Pristella Tetra, X-Ray Tetra, and Water Goldfinch.
X-Ray fish Physical Description
It is a silvery-yellow color with striking black, white, and yellow stripes on its dorsal and anal fins. The X-ray Fish is small, growing to a maximum of 1.9 inches (50 mm) in length, with females slightly larger than males.
The skin of the X-ray fish is translucent, which allows its bony internal structure to be observed. This internal structure includes its skeleton, which is visible through its skin.
X-Ray Fish Habitat & Reproduction
They are also able to thrive in more typical freshwater environments, normally in streams and tributaries during the dry season and in flooded marshlands during the rainy season.
During the wet season, the flooded environments allow the X-Ray fish to access environments otherwise not available to it. This opens up access to breeding grounds and increases the availability of food in general. It is during this season that the X-Ray fish has evolved to breed.
The X-ray fish lays eggs. While the grasslands and marshes are flooded, the X-ray fish will scatter 300-400 eggs amongst the blades of grass and other vegetation. Fry will hatch as soon as 24 hours later and are free-swimming within a few days. At this point they can access more and more food sources and develop their characteristic adult markings soon after, reaching sexual maturity by about 5-8 months of age.
Most individuals live for 3-4 years in the wild. In a fish tank, some individuals can live up to 7-8 years.
Diet & Predators
The X-Ray fish is omnivorous, feeding on a wide variety of animals and plants. Various small species of worms, aquatic insects and their larvae, and small shrimp-like animals are commonly hunted by the tetra. They will also feed on some plant and algal material to supplement their diet, but are primarily predatory.
Due to their small size, they are also susceptible to predation by a wide range of other species. Larger predatory fish will hunt virtually all species of tetra, including the X-ray tetra. Other animals are also a threat, including amphibians such as frogs as well as various bird and snake species.