Iridescent Shark: The Giant Gentle Catfish of the Aquarium World

Despite its name, the Iridescent Shark (Pangasianodon hypophthalmus) is not a shark at all, but a species of freshwater catfish. Native to the large rivers of Southeast Asia, this sleek, shimmering fish has become a common sight in pet stores. But buyer beware—while they may look like sleek mini sharks as juveniles, they grow into true river giants.

Let’s dive into the details of this impressive species and the responsibility that comes with keeping one.

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What Is an Iridescent Shark?

The Iridescent Shark gets its name from its shark-like body shape and the metallic sheen on its skin, which can reflect beautiful hues of silver, blue, and purple under the right lighting. As juveniles, they’re often sold at just 2–3 inches long, but in the wild—and in proper tank conditions—they can reach a whopping 3 to 4 feet (90–120 cm) in length!

This fish is a member of the Pangasiidae family, which includes other large, migratory catfish species. It is also known as the Sutchi Catfish or Pangasius Catfish.

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Natural Habitat and Behavior

In the wild, Iridescent Sharks are found in the Mekong and Chao Phraya river basins of Thailand, Laos, Cambodia, and Vietnam. They are migratory, traveling great distances in the wild and often schooling in large groups.

Iridescent Sharks are peaceful, social, and active swimmers, but they can be easily startled, often darting around the tank when frightened. This skittish behavior can lead to injuries in smaller tanks or tanks without adequate space.

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Aquarium Care: A Case of Mismatched Expectations

This is where many aquarists run into trouble. Despite being sold in small sizes at pet stores, Iridescent Sharks are not suitable for the average home aquarium.

Minimum Tank Requirements:

• Tank size: At least 300 gallons (1,100+ liters) for a small group

• Water temperature: 72–79°F (22–26°C)

• pH: 6.5–7.5

• Water hardness: Soft to moderately hard

• Filtration: Extremely strong, with current flow and high oxygenation

They are schooling fish, so ideally they should be kept in groups of 3 or more, which further increases the space needed.

Tank Setup:

• Large open swimming areas

• Rounded corners to reduce injury risk

• Secure, heavy-duty tank cover—they can jump

• Minimal sharp decorations (to prevent injury during darting)

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Diet

Iridescent Sharks are omnivores and not picky eaters. Their diet should include:

• High-quality sinking pellets

• Frozen or live food (bloodworms, shrimp, krill)

• Blanched vegetables (zucchini, spinach)

• Occasional fruit or plant matter

Their large size and high energy levels mean they need frequent, balanced feeding, but be careful not to overfeed.

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Lifespan and Growth

• Lifespan: 15–20 years in proper conditions

• Growth rate: Fast—can reach over a foot in just a year

• Final size: Up to 4 feet in optimal environments

Many aquarists are unprepared for this rapid growth, which often leads to stunted fish or early death when kept in undersized tanks.

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Compatibility

They are peaceful but large, so tankmates should be:

• Non-aggressive

• Too big to be considered food

• Comfortable with active swimmers

Avoid small fish (they may get eaten) or very aggressive species that may harass the Iridescent Shark.

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Ethical Considerations

Because of their impressive size and specialized needs, Iridescent Sharks are best suited for public aquariums or experienced hobbyists with very large tanks. Sadly, many end up in unsuitable environments or are surrendered when they outgrow their tanks.

If you're interested in their beauty and movement, consider smaller alternatives like:

• Bala Sharks

• Silver Dollars

• Tinfoil Barbs (though still large)

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Final Thoughts

The Iridescent Shark is a breathtaking species that deserves admiration and respect—but not impulsive purchasing. While their shimmering beauty and shark-like shape may be tempting, their enormous adult size, energetic swimming behavior, and social needs make them a long-term, space-demanding commitment.

If you're ready for a true freshwater giant and have the space to match, the Iridescent Shark can be a centerpiece in a well-designed, massive community tank.

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