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Redtail Catfish

Phractocephalus hemioliopterus

The 'Puppy Dog' Monster of the Amazon (120-130 cm / 4+ feet). The most famously tragic victim of the aquarium industry. As a 2-inch baby in the pet store, it is unimaginably cute, colorful, and active. However, it explodes in growth faster than almost any other fish, transforming into a massive, 80-pound, 4-foot-long bulldozer with an endlessly cavernous, vacuum-cleaner mouth. While incredibly peaceful and famously 'friendly' (often begging for food like a dog), it will blindly and effortlessly swallow absolutely ANY tankmate that can physically fit inside its massive, yawning maw. It strictly requires indoor ponds or colossal 1000+ gallon acrylic mega-tanks.

Taxonomy

Class:Actinopteri

Order:Siluriformes

Family:Pimelodidae

Genus:Phractocephalus

Species:Phractocephalus hemioliopterus

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Water Temperature

22 - 28 °C

pH Value

6 - 7.5

Water type

Freshwater

Tank level

Bottom

Adult size

130 cm

Minimum tank volume

>= 500 L

Minimum group

>= 1

5 - 20 dGH

2 - 10 dKH

TDS

95 - 400 ppm

Conductivity

148 - 625 uS/cm

Species description

Geographical Origin and Habitat: Vastly native to the main river channels, incredibly deep, murky muddy pools, and sprawling flooded jungles of the Amazon, Orinoco, and Essequibo river basins in South America. They are the undisputed apex bottom-scavengers of the 'White Waters' (rivers thick with suspended mud). Because visibility is practically zero in these rivers, their eyes are small and relatively weak; they hunt entirely by dragging their incredibly long, highly sensitive sensory 'whiskers' (barbels) across the muddy bottom to blindly smell and feel for dead fish, crustaceans, and slow-moving prey in the dark.

Taxonomy and Morphology: The Shovel-Headed Titan (Pimelodidae). A massive, heavily-built, scaleless 'long-whiskered' catfish. It is built like a submarine. The front half of the body is incredibly wide, thick, and flattened, culminating in a massive, bony, square-shaped head that looks like a shovel. The mouth is an astonishingly huge, rubbery, cavernous trap-door extending all the way across its wide face. It has three pairs of long, elegant barbels: two incredibly long, stiff sensory whips stretching from its upper jaw all the way down its back, and four shorter ones under its chin. It lacks scales completely, instead wrapped in a thick, leathery, slimy, mucus-coated skin to slip through roots and mud.

Social Behavior: The 'Gape-Limited' Friendly Giant. Their personality is why people buy them and refuse to give them up. They are incredibly docile, lazy, and deeply 'affectionate' for a fish. They quickly learn to recognize their owner, will rush to the glass, and readily accept food directly from your hand, acting like giant aquatic puppies. HOWEVER, THE FATAL FLAW: They are 'gape-limited' predators. They are not aggressive or mean, but they are mindless vacuums. If they are hungry at 3 AM and bump into a sleeping, peaceful tankmate, and that tankmate happens to be small enough to squeeze through the catfish's massively expandable lips. they will simply inhale it and go back to sleep. They do not 'attack', they just blindly swallow.

Coloration and Sexual Dimorphism: The Tri-Color Masterpiece. It is arguably the most stunningly beautiful, vividly colored giant catfish in the world. The massive, bony head, back, and upper flanks are a dense, velvety, solid dark chocolate-brown or deep olive-black. In striking, beautiful contrast, the entire massive, flat belly and lower jaw are a pure, brilliant, glowing milk-white. A jagged, faded yellowish-cream stripe separates the two halves. THE SIGNATURE CROWN: The massive, thick, fleshy tail fin (and sometimes the tips of the dorsal fin) is a blinding, vivid, fiery cherry-red or bright orange, earning it its famous name. Males and females look completely identical to the human eye.

Care, breeding and tankmates

Aquarium Setup: The 'Pond or Bust' Reality (Colossal Footprint Required). NEVER buy this fish if you only have a 'big' 150-gallon tank. An adult requires an absolute minimum of an indoor heated tropical pond or a custom acrylic vault measuring AT LEAST 10-12 feet long and 4-6 feet wide (1,500 to 3,000+ gallons). They are clumsy, heavy bulldozers. If kept in a tight tank, they will violently smash into glass heaters, crush filters against the wall, and knock over massive rocks, destroying the tank. THE SAND MANDATE: You MUST use bare bottoms or ultra-fine, soft sand. Jagged, sharp gravel will brutally scrape and slice their soft, scaleless white bellies, causing horrifying, fatal bacterial ulcers and massive fungal rot.

Diet and Feeding: The Bottomless Trash Can (Voracious Benthic Carnivore). Feeding them is incredibly easy and fun; they will eat until their stomachs bulge like balloons. As babies, feed massive whole earthworms, live bloodworms, and small shrimp. As massive adults, they require colossal meals: massive, whole, raw white-fish fillets (tilapia, cod, smelt), giant whole raw prawns with the crunchy shell left on, and entire squid. They eagerly inhale massive, sinking jumbo Carnivore Pellets. THE DEADLY FAT WARNING: NEVER feed them warm-blooded mammal meat (beef heart, chicken) or cheap live feeder goldfish. The fat will permanently clog their livers, causing obesity, fatty liver disease, and a tragically early death.

Water Quality: The Biological Nightmare (Ammonia Factory). While they are very physically hardy and tolerate a wide range of warm, tropical Amazonian conditions (24-28°C / 75-82°F) and slightly acidic to neutral pH (6.0-7.0), keeping the water clean is an absolute nightmare. A 50-pound carnivorous fish eating pounds of raw fish meat every week produces catastrophic, unbelievable amounts of rotting fecal waste and liquid ammonia. A standard canister filter is a joke to them. You absolutely MUST employ massive, industrial-grade Pond Bead Filters or colossal Sump systems, combined with brutal, back-breaking 50% weekly water changes, or they will suffer severe ammonia burns, lethargy, and barbel rot.

Compatibility and Cohabitation: THE 'SWALLOW WHOLE' TRAGEDY AND THE MEGA-VIP TANKMATES. They are exceptionally peaceful, gentle giants. to things they cannot eat. They beautifully co-habitate in massive millionaire mega-tanks with other absolutely giant, un-swallowable monsters: massive Pacus, adult Arowanas, giant Datnoids, and giant Freshwater Stingrays (though rays risk getting sucked on). THE HEARTBREAKING NOVICE MISTAKE: Their mouths are deceitfully huge and stretch like rubber. A 24-inch Redtail Catfish will effortlessly and blindly inhale a massive 8-inch Oscar, a 6-inch Severum, or a $100 school of adult Silver Dollars while you sleep, leaving you with an empty tank and a very fat, happy catfish the next morning. Only keep them with fish that are at least HALF the length of the Redtail's entire body.

Aquarium Breeding: The Massive Mud Pond Miracle (Impossible in Home Aquaria). Breeding Redtail Catfish in a glass home aquarium is totally impossible, completely undocumented, and pure fantasy. The only places they are bred are massive, commercial outdoor mud-pond facilities in South America and Asia. The farmers must wait for the fish to become massive, sexually mature adults, and then strictly inject the fish directly with artificial hormones (pituitary gland extract) to force them to spawn. They release hundreds of thousands of sticky, yellowish eggs into the muddy water, completely ignoring them afterward, leaving the tiny, fragile fry to hatch and immediately start blindly hunting worms in the mud.

Risks and Diseases: 1. THE STUNTED DEFORMATION TORTURE (Spinal Crushing/Stunting): The most common, cruel, and tragic fate for 99% of pet store Redtails. The ignorant owner keeps the massive, explosively growing fish locked in a 75-gallon or 125-gallon tank. The fish's organs continue to grow, but its spine hits the glass. The spine horribly permanently bends into a 'U' or 'S' shape, crippling the fish, crushing its internal organs, and dooming it to a slow, agonizing, toxic death by biological suffocation in its own waste. 2. INTESTINAL IMPACTION (The Gravel Killer): Using cheap, colorful, chunky gravel instead of soft sand. The blind, vacuum-feeding catfish inhales a shrimp, accidentally sucks up a giant chunk of rock, and swallows it. The rock becomes permanently, fatally lodged and impacted in the fish's intestines, causing a horrific, agonizing, incurable death by internal blockage, severe bloating, and torn bloody intestines. 3. BARBEL ROT (Sensory Amputation): Letting the water quality decay with high nitrates. The ammonia burns off the fish's delicate sensory 'whiskers' (barbels). They become infected, turn white with fungus, and rot completely off, leaving the fish permanently blind, unable to smell food, stressed, and severely depressed.

Geographic Origin and Distribution

Vastly native to the main river channels, incredibly deep, murky muddy pools, and sprawling flooded jungles of the Amazon, Orinoco, and Essequibo river basins in South America. They are the undisputed apex bottom-scavengers of the 'White Waters' (rivers thick with suspended mud). Because visibility is practically zero in these rivers, their eyes are small and relatively weak; they hunt entirely by dragging their incredibly long, highly sensitive sensory 'whiskers' (barbels) across the muddy bottom to blindly smell and feel for dead fish, crustaceans, and slow-moving prey in the dark.

Origin

Amazon, Orinoco, and GuianasNorth America

Fish profile

Temperament: Semi-aggressive
Diet: Omnivore
Sex ratio: Solitary
Feeding frequency: Twice daily
Bioload: The Redtail catfish produces an absolutely massive bioload due to its enormous adult size and hearty appetite. Only the most robust, heavy-duty commercial or custom filtration systems can handle their waste output. Huge and frequent water changes are mandatory to prevent toxic spikes.
Flow: Stagnant
Reproduction: Oviparous
Compatibility & tankmates: This is a highly predatory fish that will eat absolutely anything that fits into its incredibly large mouth. They should only be housed with other giant, robust species that are too large to be considered food. Smaller tankmates, even medium-sized cichlids, will eventually be consumed.
Tank level: Bottom

FishBase

Window to the official scientific data of the species

Data synced on: 06/15/2026

Scientific Parameters & Models

Trophic level: 4.2 ± 0.73 se
Resilience: Low (4.5 - 14 years)
Phylogenetic uniqueness (PD50): 1
Bayesian Length-Weight: a = 0.00912, b = 3.07

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.

Variants and close relatives

Same atlas type, nearby scientific identity, genus, or family.

Spotted Shovelnose Catfish

Pseudoplatystoma corruscans

Species description

Care, breeding and tankmates