X Ray Fish: A Transparent Guide to Breeding, Diet, and Tank Life

You’re going to dive into the realm of a fish with its skeleton on the outside! Yes, I’m talking about the X ray fish, a spellbinding little wonder whose crystal-clear body allows you to peek into its inner world like a living X-ray! Believe me, this transparent journey is about to get fin-tastic! Let’s go deep into its aquatic life story, from its shimmering scales to its astonishing resilient spirit.

X Ray Fish photos
KingdomPhylumClassOrder FamilyGenusScientific Name
Animalia ChordataActinopterygiiCharaciformesCharacidaePristellaPristella maxillaris
Taxonomic Classification of X Ray Fish (Pristella maxillaris)

Origin and Evolution

Evolutionary History

Regarding x ray tetra origin, it belongs to the Characidae family, which has a rich fossil record dating back to the Paleocene epoch – around 66 million years ago. Genetic analysis propose the x-ray tetra lineage branched off other Characins about 15 million years back in time. Studies pinpoint the closest relative as the genus Hyphessobrycon.

Genetic Composition and Diversity

X-ray tetras have a diploid chromosome number of 2n = 50, distributed across 24 pairs. In comparison with other Characins, this’s a relatively low number. X-ray fish population shows some genetic diversity although a single species. Research has pinpointed variations in mitochondrial DNA proposing distinct genetic lineage within the species.

Environmental Adaptations

  • Translucent Body: Transparency acts as a pivotal camouflage defense against predators; it also allows efficient light penetrations for internal organs.
  • Small Size: X-ray tetras– averaging just 5cm in length – maneuver impeccably through the dense vegetation of their native streams and tributaries.
  • Omnivorous Diet: The X ray tetra diet of small invertebrates, algae and detritus lets them exploit a plentiful food sources and survive in fluctuating environmental conditions.

Distribution and Population

Geographic Range

Touching upon x ray fish distribution, its reign stretch across portions of South America, chiefly located in the coastal drainages of northeastern Brazil, Guyana and Venezuela. Their ancestors once roamed a broader territory, potentially including parts of Colombia and Peru.

Population Dynamics

Though we don’t get full picture of x ray tetra population, studies in certain Brazilian streams found densities exceeding 100 individuals per square meter!


Continent(s) South America
CountriesBrazil, Guyana, Venezuela
Bio-geographical RealmsNeotropical
Biome Freshwater: Clear streams, tributaries, flooded marshlands
Climate ZonesTropical wet and dry: Warm temperature range (21-28°C)

Types of Tetra

The X-Ray tetra, first described by Albert Ulrey in 1894, has stolen the spotlight, albeit there’re around 150 other tetra species. Among these, the most conspicuous tetra types are:

  • Black Neon Tetra (Hyphessobrycon herbertaxelrodi)
  • Bloodfin Tetra (Aphyocharax anisitsi)
  • Buenos Aires Tetra (Hyphessobrycon anisitsi)
  • Congo Tetra (Phenacogrammus interruptus)
  • Ember Tetra (Hyphessobrycon amandae)
  • Emperor Tetra (Nematobrycon palmeri)
  • Lemon Tetra (Hyphessobrycon pulchripinnis)
  • Neon Tetra (Paracheirodon innesi)
  • Rainbow Tetra (Nematobrycon lacortei)
  • Ruby Tetra (Axelrodia riesei)


X ray tetra Habitat

Habitat Preferences

With reference to x ray fish habitat, they prefer shallow, well-vegetated waters with soft substrates such as leaf litter and fallen branches. These species thrive in warm, tropical environments; ideal water temperatures range from 21-28°C (70-82°F), with slightly acidic pH levels (6.0-6.5).

Habitat Utilization Patterns

Just like most Characins, x ray tetra fish are diurnal, implying they’re most active over the span of the day. In the course of the wet season, rising water levels flood surrounding flood plains, constructing new foraging grounds and igniting reproductive seasons.

5 X-Ray Fish Facts

  • Their namesake comes from their translucent skin, unfolding their silvery bones and organs beneath.
  • Notwithstanding the x-ray tetra body is practically see-through, its fins shimmer with a golden iridescence.
  • X-Ray tetras, being agile swimmers, darting and weaving, are capable of leaping out of the water to snatch insects.
  • They prioritize dimly lit, plant-filled environments to scatter their eggs, and even then, raising the fry can be tricky.
  • They make use of their acute sense of hearing to pinpoint food!


X ray tetra Appearance

When it comes to x-ray fish appearance, it’s aptly entitled for its translucent skin that unfolds its inner workings. Let’s dive into the other aspects of its appearance.

Physical Characteristics

  • Size: Concerning the x ray fish size, they are petite beauties, reaching a maximum length of around 1.8 inches (4.5 cm).
  • Shape: Their bodies are slender and streamlined, having a slightly compressed shape from the sides.
  • Color: The x ray tetra’s skin, magnificently translucent, shimmers with a silvery-yellow hue, oftentimes outlined as almost golden in certain lighting.
  • Markings: Accumulating a splash of vibrancy are the stunning yellow, white and black stripes embellishing their dorsal and anal fins.
  • Distinctive Feature: It is the x-ray tetra’s transparent skin that makes it strikingly conspicuous. This unparalleled adaption permits them to blend effortlessly into their natural environment.

Sexual Dimorphism

There’re subtle differences that appear upon closer look of both sexes. Male x ray tetras are somewhat smaller and slimmer that females. Their bodies are relatively more streamlined, while females showcase a more rounded belly, exclusively when gravid (carrying eggs). On the related note, got the scoop of the oarfish?


Color(s) Silverish-yellow body with iridescent sheen; red-tipped tail 
TongueProtrusible, toothless   
MouthUpward-facing, small terminal mouth  
Jaw Delicate, lacks strong teeth for predation
TeethMinute, used for scraping algae and biofilm        
NosePaired nostrils located above snout
FinsPelvic fins paired, ventral, modified into long filaments
Skeleton Visible through semi-transparent body

Reproduction and Life Cycles

Mating System

In light of x ray fish mating strategy, studies propose that these species engage in a dynamic polygamy system, whereby males may mate with multiple females and vice versa.

Reproductive Biology

In their South American homeland, the breeding season accords with rainy season. Ignited by increased water flow and nutrient accessibility, x ray tetras take part in pair spawning. Males exhibit vibrant colors and perform elaborate fin sweeps to appeal females.

When the courtship dance is over, the female scatters between 300 and 400 adhesive eggs among aquatic vegetation. Once fertilized, these eggs are left to fend for themselves.


Eggs hatch within 25 hours with optimal water conditions, releasing tiny, translucent fry. These delicate hatchlings rest upon yolk reserves for the first few days before progressing into feeding on microorganisms and infusoria.

Life Cycle Stages

The x ray fish life cycle adventure from fry to adult is interposed with distinct stages:

  • Fur: At first, measuring just 2 to 3 millimeters, these translucent fry are vulnearable to predations.
  • Juvenile: Fry become more active and adventurous swimmers as they grow and feed.
  • Adult: X-ray tetra, reaching sexual maturity at around 3 to 4 months of age, obtain their full adult size and lively coloration.

Mating Habits

Mating BehaviorMorning frenzy, males chase & nudge females to release eggs
Reproduction SeasonRainy season
Litter Size200-300 scattered among plants or on dedicated mops
Hatch Time24-48 hours, tiny & transparent at first
Independent AgeFew days, but remain vulnerable for a while

Diet and Lifestyle

fish photos

Feeding Ecology

X-ray tetras, being opportunist omnivores, are chiefly typified as secondary consumers. While they graze on plant matter like algae and biofilm, their diet predominantly comprises a diverse range of small invertebrates, such as insect larvae, micro-crustaceans like copepods and zooplankton.

Foraging Strategies

These nimble predators exert a highly sophisticated foraging technique. They swim in tight-knit shoals, creating a “living net” that sweeps through aquatic vegetation. This coordinated movement excellently dislodges concealed prey.

Diurnal Activity Patterns

X-ray tetras are exclusively diurnal creatures, most active in the course of the day. As sunlight filters through the water, they appear from their nocturnal shelters among the plants and start their foraging.

Threats and Conservation

Touching upon x ray fish conservation status, the species has not been listed on the IUCN Red List that is under threat in its environments; nonetheless, they’re vulnerable to predation by a plethora of other species, particularly those that hunt virtually all species of tetra, including the x-ray tetra.

Cultural Significance and Symbolism

The x-ray tetra represents the mythical Tucano – a shapeshifting creature capable of seeing through obstacles. The transparency of the fish mirrors the Tucano’s capability to perceive hidden worlds, personifying wisdom and insight.

The Takeaways

Forge a path through an intriguing journey as we unfold fascinating facts about x-ray tetras – truly captivating animals that start with X. Join us in shedding light on their remarkable rundown!

Common NameX-Ray Fish
Other Name(s)X-Ray Tetra, Golden Pristella Tetra, Water Goldfinch, Pristella Tetra
Number of Species 1
Population SizeWidespread and locally abundant
Lifespan 4-6 years in captivity
Weight Less than 0.5 grams   
Length Up to 5 cm (2 inches) 
Predator Larger fish, birds, aquatic invertebrates     
Prey Small invertebrates, algae, detritus 
Most Distinctive FeatureTranslucent body revealing internal organs


The X-Ray Fish is a small schooling aquatic fish that inhabit the Amazon basin in South America.

A nurtured -for x-ray tetra can live from 4 to 5 years. Though these x-ray tetras are hardy, their lifespan depends on the care you offer.

The x ray tetra is located in the Amazonian coastal waters of Brazil, Guyana, and Venezuela in South America.

Mudassar Ahmad

He is a seasoned blogger since 2012 and an M.Phil graduate in English Linguistics. He captivates readers with his eloquent prose and insightful perspectives. His passion for language and dedication to crafting compelling content make him a trusted voice in the online sphere. Explore the world through Ahmad's literary lens.

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