Iridescent Shark (Pangasius Catfish / Basa)
Pangasianodon hypophthalmus
The Pet-Store Tragedy and the False Shark (100-130 cm / 3-4 feet, up to 100 lbs). This species represents the absolute pinnacle of irresponsible aquarium industry marketing. Sold to millions of unknowing beginners as an adorable, 2-inch 'shark' with shimmering rainbow scales, it is actually a massive, migratory Asian river catfish and a highly skittish, panic-prone schooling giant. It explodes in growth, reaching over 3 feet and weighing up to 100 pounds. It loses all rainbow color, becoming a massive, grey, blob of fat. They are categorically unsuitable for ANY home aquarium and strictly require 5,000+ gallon heated indoor ponds to prevent horrific spinal deformities or death by repeatedly smashing their skulls into the glass in sheer panic.
Water Temperature
24 - 28 °C
pH Value
6.5 - 7.5
Water type
Freshwater
Tank level
Middle
Adult size
130 cm
Minimum tank volume
>= 500 L
Minimum group
>= 1
GH
5 - 20 dGH
KH
2 - 10 dKH
TDS
95 - 400 ppm
Conductivity
148 - 625 uS/cm
Species description
Geographical Origin and Habitat: The King of the Mekong. Endemic to the incredibly massive, deep, fast-flowing, and immensely turbid main river channels of the Mekong and Chao Phraya river basins across Southeast Asia (Thailand, Vietnam). They are monumental migratory fish. During the flood season, massive schools of these giants travel hundreds of miles up the deep, murky rivers to spawn in the flooded plains. They are biologically programmed to swim tirelessly in open water, making confinement in a glass box a form of psychological torture.
Taxonomy and Morphology: The Scaleless River Whale (Pangasiidae). It is a 'Shark Catfish', completely unrelated to true marine sharks. However, it earns its name because it has a high, prominent, erect dorsal fin, a deeply forked tail, and an incredibly active, pelagic, mid-water 'shark-like' swimming style. The body is completely scaleless (smooth and slippery). The head is massive, blunt, and slightly flattened, with small eyes set low and tiny barbels. As adults, they completely lose their sleek, shark-like profile, blowing up into incredibly deep, fat, massively heavy, blob-like titans of pure meat (this is the exact species heavily farmed and sold in grocery stores globally as 'Swai' or 'Basa' fish fillets).
Social Behavior: The Hysterical Panic Shoal. Despite growing to 100 pounds, they are heavily preyed upon in the wild when young and are biologically hardwired as highly nervous, skittish schooling fish. They absolutely must be kept in groups. THE CAPTIVE NIGHTMARE: In a glass box, their flight response is catastrophic. A sudden loud noise, a shadow, or turning the room light on will trigger a hysterical, blind, explosive panic attack. The massive, 3-foot fish will dart at breakneck speed, blindly smashing and slamming violently into the glass, the decorations, the heater, and each other, often knocking themselves unconscious, ripping their own flesh open, or playing dead on the bottom of the tank in sheer terror.
Coloration and Sexual Dimorphism: The Rainbow Deception and The Grey Reality. The reason they are sold in pet stores is their juvenile phase (2-4 inches): they are mesmerizing. Their backs are a sleek, steely blue-black with bright silver stripes, and under the light, their scaleless skin flashes with an intense, glowing, holographic rainbow iridescence. THE UGLY TRUTH: As they grow past 12 inches, the magical rainbow iridescence and the stripes completely and permanently vanish. The massive adults become extremely drab, boring, monotonous shades of dark slate-grey, charcoal, or muddy silver with a massive, flabby white belly. An albino variant (yellowish-pink body, red eyes) is also heavily sold. Males and females look completely identical.
Care, breeding and tankmates
Aquarium Setup: The Absolute 'Ponds Only' Mandate (No Aquariums). It cannot be overstated: keeping a 3 to 4-foot, highly skittish schooling torpedo in a 75-gallon or 125-gallon glass tank is horrific animal abuse. They demand a massive, heated, custom indoor tropical pond or monumental acrylic enclosure stretching a minimum of 15 to 20 feet long (5,000 to 10,000+ gallons) to allow their school to swim without smashing the walls. THE EMPTY VOID RULE: The pond must contain zero decorations in the center swimming lane. No rocks, no driftwood, no hard objects. Use ultra-fine soft sand only. If they panic, they will blindly impale themselves or scrape their delicate scaleless skin off on any hard object, dying of massive fungal infections.
Diet and Feeding: The Bottomless Benthic Vacuum (Omnivorous Scavenger). They are not active hunters, but rather massive, blind biological vacuums. In the wild, they filter through the mud for worms, decaying plants, and dead fish. In captivity, they are incredibly greedy gluttons. Feed them massive amounts of sinking Jumbo Koi/Pond Pellets, spirulina discs, blanched zucchini, and whole thawed shrimp or white fish. DEADLY WARNING: Do not overfeed them meat or live feeder fish. In captivity, without the ability to swim hundreds of miles, they are insanely prone to morbid obesity, developing horrific, massive bulges of fat around their organs that will eventually cause fatal heart failure and lethargy.
Water Quality: The Heavy Filtration Pond Demand. A massive school of 50-pound fish produces a truly staggering biological load of ammonia and feces. Standard canister filters will be completely useless. You must run heavy-duty, industrial Pond Bead Filters, massive Sump systems, and perform grueling 50% weekly water changes to prevent the water from turning foul. While they tolerate low oxygen in the muddy Mekong, in a closed pond, poor water quality will immediately cause their sensitive, scaleless skin to burn and peel. They require hot tropical water (24-28°C / 75-82°F) and tolerate a wide pH range (6.5-7.5).
Compatibility and Cohabitation: The Gentle, Clumsy Giant (Elite Monster Comm Only). It is an incredibly peaceful, utterly indifferent giant that has zero aggressive or territorial instincts. In an appropriately massive, millionaire-level pond, they peacefully coexist with other massive, armored giants: giant Pacus, colossal adult Oscars, or massive plecos. THE ACCIDENTAL GULP DANGER: While they don't hunt, their mouths are enormous. Any small or slender fish (tetras, small corydoras, guppies) will be accidentally inhaled and swallowed whole like a piece of popcorn while the massive Pangasius blindly vacuums the bottom of the pond during feeding time. Small tankmates are guaranteed to disappear.
Aquarium Breeding: The Massive Aquaculture Mud-Farm (Zero Captive Breeding). Completely, utterly impossible in a home aquarium. Successful breeding of this massive, migratory river species only occurs in monumental, multi-acre outdoor mud ponds in Asian commercial aquaculture farms (primarily in Vietnam along the Mekong Delta). It is an incredibly lucrative global food industry. Farmers capture the massive adults, inject them with artificial pituitary hormones, and spawn millions of eggs to be raised as 'Basa' food fish for the supermarket. A tiny fraction of these millions of fry are heartbreakingly diverted to the global pet trade to be sold to unknowing hobbyists.
Risks and Diseases: 1. THE STUNTING SPINAL DEFORMATION (The 'U-Bend' Torture Death): The most common, cruel, and tragic end for this species. Kept in a cramped 55-gallon glass box, the rapidly growing, massive fish hits the walls. Unable to grow lengthwise, the immense pressure of its growing muscles crushes its own spine, permanently bending the fish into a horrific, agonizing 'U' shape. The internal organs are crushed, and the fish slowly suffocates and starves in intense pain, dying a stunted, death. 2. PANIC SKULL FRACTURE (Collision Fatality): Highly skittish, the fish panics at a sudden light, explodes in a blind 30 mph sprint, and brutally smashes its massive head into the glass or heater, fracturing its skull, tearing its scaleless face open to fatal fungal infection, and dying of shock.
Geographic Origin and Distribution
The King of the Mekong. Endemic to the incredibly massive, deep, fast-flowing, and immensely turbid main river channels of the Mekong and Chao Phraya river basins across Southeast Asia (Thailand, Vietnam). They are monumental migratory fish. During the flood season, massive schools of these giants travel hundreds of miles up the deep, murky rivers to spawn in the flooded plains. They are biologically programmed to swim tirelessly in open water, making confinement in a glass box a form of psychological torture.
Origin
Selective breeding and cultivarsSouth and Southeast Asia
Fish profile
- Temperament
- Semi-aggressive
- They are extremely skittish and easily frightened by sudden movements. When spooked, they will blindly ram into the aquarium glass. Their nervous temperament makes them poorly suited for standard home setups.
- Diet
- Omnivore
- They are highly omnivorous and will consume almost anything. Quality large pellets and meaty foods form the base of their diet. As they mature, adding vegetable matter is beneficial.
- Life expectancy
- 15-20 years
- In an ideal and spacious environment like a large tropical pond, Pangasianodon hypophthalmus can live for a period of 15 to 20 years. Unfortunately, in common home aquariums, their lifespan is drastically reduced due to induced stunting and head trauma from crashing into the glass. Providing a tank of adequate dimensions is the primary factor in preventing premature death due to chronic stress.
- Adult size
- 130 cm
- The catalog's scalar value is 130 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 130 cm for this species, recorded as standard length (SL). The taxonomic record consulted is Pangasianodon hypophthalmus (v25.04); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
- Sex ratio
- Solitary
- They are schooling fish that feel safest in large groups. Keeping them singly causes extreme stress and erratic behavior. However, a school of adults requires an aquarium of thousands of gallons.
- Feeding frequency
- Twice daily
- Young fish should be fed heavily multiple times a day. Adults require substantial meals several times a week. Their voracious appetite leads to incredibly rapid growth.
- Bioload
- They produce a staggeringly massive bioload. Their rapid growth and immense adult size mean they output huge waste volumes. Commercial-grade filtration is often required for adult specimens.
- Flow
- Stagnant
- They prefer moderate to high flow that mimics large river systems. Strong water movement helps keep them exercised. Excellent oxygenation is mandatory for their active lifestyle.
- Reproduction
- Oviparous
- Captive breeding is completely impossible in standard home aquariums. They are bred exclusively in massive commercial ponds using hormone injections. They require extensive river migrations to naturally spawn.
- Compatibility & tankmates
- They will enthusiastically eat any fish small enough to fit in their mouths. They are generally peaceful with similarly sized, robust giants. They panic easily and can severely injure delicate tank mates during frantic dashes.
- Tank level
- Middle
- They are highly active mid-water swimmers. They constantly cruise back and forth in the middle zones of the tank. They need massive amounts of unobstructed open swimming space.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 3.1 ± 0.46 se
- Resilience
- Low (4.5 - 14 years)
- Phylogenetic uniqueness (PD50)
- 0.75
- Bayesian Length-Weight
- a = 0.00479, b = 3.11
- VulnerabilityVery high vulnerability (90 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
Related species
Recommendations grouped by close relatives, companion choices, and similar care.
