Iridescent Shark 101: Care, Growth Rate, Size, & More

The iridescent shark aka iridescent catfish is a very large freshwater fish that only the most prepared aquarists should keep.

While a lot of the care requirements aren’t that complicated, it’s not worth attempting to own one of these if you don’t have the space and resources to do so. These fish need large tanks if you want them to live happy and healthy lives.

This means if you don’t have room or don’t want to spend the time and money maintaining a big aquarium, they aren’t for you.

With that being said, owning one of these fish can be a bunch of fun (and quite rewarding). If you’re interested in owning an iridescent shark and are willing to do what’s necessary to care for them you’ve come to the right place.

In this guide, we cover everything you need to know about iridescent shark care. Ideal food, compatible tank mates, their growth rate, and more.

You’ll be an expert by the time you’re finished reading this!

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Species Summary

The iridescent shark (Pangasianodon hypophthalmus) goes by a few different common names such as the iridescent catfish, sutchi catfish, and the siamese shark.

Despite what their common name might indicate, these are not man-eating killers of the deep! In fact, they belong to the Pangasiidae family which is comprised of shark catfish. Regardless, they’re always included on every list of aquarium-friendly freshwater sharks.

An iridescent shark swimming in a freshwater aquarium

You can find iridescent sharks scattered throughout Southeast Asia. They’re a tropical freshwater fish that tend to stick to deep and wide rivers where they have enough room to roam freely.

They are condensed in two of the largest rivers in Southeast Asia, the Mekong, and Chao Phraya. These massive rivers are perfect because they allow them to cover significant ground when they migrate at different times of the year.

Iridescent sharks are commonly fished and grown for food in certain areas due to their size and affordability. The name on the food market for these fish is swai.


The lifespan of an iridescent shark is upward of twenty years. This is another reason why understanding their size and growth rate is so essential.

These are fish that can live a very long time if you provide them with the right environment. Doing anything otherwise is unfair, and will shorten their lifespan significantly.


Iridescent catfish are rather interesting looking animals. While some people think of many catfish as being a little uninspiring in the aesthetics department, it’s hard to argue with the unique look you find with these fish!

One of the things that stands out right away is their unique dorsal fin. It’s shaped like a sail and will fan out or tuck back depending on how the fish is swimming.

Iridescent sharks also have very dark shiny skin when they’re younger. As they grow older their skin becomes less shiny and transitions into a dark, solid grey. This can sometimes confuse people who see them as adults and lead to misidentification.

These fish have long barbels that give them the classic “catfish” look. These help them navigate in waters where there’s low visibility.

One thing you’ll notice is that these fish have rather large eyes! This is especially pronounced when they’re younger (they sort of grow into them as they age).

Their caudal fin has the same semi-flappy, sail-like tissue that you find on their dorsal fin. Their anal fins extend from the flat part of their belly to the bottom part of their caudal peduncle.

When determining if an iridescent shark is a male or female the biggest thing to look for is their size. Females are a bit wider and less streamlined than males.

Albino Iridescent Shark

It’s also possible to find albino iridescent sharks from various sellers. These are highly sought after and can sometimes be difficult to find in certain parts of the world.

The albino iridescent shark

An albino iridescent shark is built exactly like a regular one. The only difference is it’s white all over and has red eyes.


The average iridescent shark size can reach 3-4 feet in length when fully grown. We weren’t kidding when we said these fish can get quite large!

Their size is one of the biggest problems that owners have to navigate. These fish often get purchased by people who don’t understand their maximum size and growth rate. This leads to the health of the fish suffering, or the owners having to give them away.

Make sure you’re prepared to house a fish of this size before you consider getting one. While iridescent sharks are fun and exciting animals to own, they’re not for everyone.

Iridescent Shark Care

Iridescent shark care is interesting. It’s actually rather manageable when it comes to their actual water parameters, food, and tank mates.

The biggest thing you need to deal with is their size. As we’ve already established, these fish can get quite big. That means you need to provide them with a large enough tank for them to be comfortable and healthy.

That’s actually the biggest mistake we see owners of these fish make. They see them when they’re small and think that a 40-gallon tank will be enough. Then when the fish grows everything about their care plan starts to fall apart.

Read through the essentials of iridescent shark care and make an honest assessment if you’re prepared to deal with them as they grow.

Tank Size

When fully grown you’ll want at least a 300-gallon tank for an iridescent shark. This will give them enough room to swim freely and be comfortable.

Some owners keep these fish in smaller tanks when they initially get them and gradually transition them to larger and larger tanks over time. While this is a viable strategy it’s important to make the switch BEFORE they need it, not after.

Too often owners realize they need an upgrade after their poor fish has been cramped for a month or two. Then it takes another couple weeks for them to get a new tank and move them over.

Always try to think ahead to maximize the comfort and health of your fish. You’re going to need to get a larger tank eventually, so you might as well be prepared!

Author Note: These are schooling fish that do much better when in a group. If you want to reduce stress and maximize their happiness you’ll need to increase their tank size for each additional fish you add.

Water Parameters

Iridescent catfish are rather hardy which gives you some flexibility when it comes to their water parameters. It shouldn’t be a problem to maintain the ranges listed below.

  • Water temperature: 72°F to 79°F
  • pH levels: 6.5 to 7.5
  • Water hardness: 2 to 20 dGH

Even though these are hardy fish you should always make sure to monitor the water conditions regularly. In larger tanks it can take longer to correct these levels. This especially holds true if you don’t have much experience with big tanks as well.

It’s always easier to catch things before they become a problem than try and fix them once everything has gone awry. 

What To Put In Their Tank

When it comes to setting up their tank you’ll want to mimic the rivers they come from as much as possible. Like we said earlier, iridescent sharks are naturally found in deep large rivers in Southeast Asia.

You’ll only want to add things to the base of their tank and make sure they have enough room to swim above that. An overdecorated tank is the last thing large fish like this need!

Our favorite things to add to their tank are driftwood and decent-sized rocks. This is what the riverbeds are covered with in their natural habitat.

It’s also recommended to keep their tank in a quiet area of your home. These fish are easily startled and a lot of surrounding noise or movement can cause a lot of unnecessary stress.

Author Note: Don’t worry too much about plants. Even though they can positively impact the quality of your water, it’s not something these fish are used to. They won’t get any value out of small plants at the bottom, and tall plants that reach the surface will only get in their way.

Common Possible Diseases

While there aren’t any species-specific diseases you have to worry about with iridescent shark, you still need to keep an eye out for common afflictions. Since these catfish don’t have scales it makes them a little more susceptible to various skin conditions. 

Ich is probably the most likely disease they’ll face. Due to their coloration, it should be pretty easy to notice and treat.

However, it’s far better to prevent these kinds of illnesses from happening in the first place. Monitor and maintain the quality of the water in your tank and the chance that your fish gets sick will go down significantly.

Food & Diet

Finding the right iridescent shark food is all about maintaining variety. Since these fish are omnivores (and catfish) they’re really not picky when it comes to their diet.

That means it’s on you to find the right combination of food that gives them the necessary vitamins and nutrients to stay healthy. Micronutrient deficiencies can impact the health of your fish and shorten their lifespan, so spending some time to come up with a diet plan is the right thing to do.

A flake-based diet is usually recommended as long as it’s from a high-quality company. This will cover their base needs, grow, and fight off potential diseases.

In addition to this, you’ll want to throw in some live food as well. Not only will this help provide them with the extra protein they need (these are big fish after all), it will give them a source of enrichment.

Some great options are:

Make sure you’re getting your iridescent shark food from reputable and trusted sources. A common way for diseases to enter an aquarium is through low-quality foods, so do some research first!

Behavior & Temperament

Iridescent sharks are a rather jumpy fish that can get spooked rather easily. When you combine this with their size it can result in quite a lot of movement!

These are schooling fish that do much better in groups. When alone they’re far more likely to be stressed and nervous but in a group, they’re much calmer. If you’re keeping them alone (which we don’t recommend) you’ll notice much more shy and nervous behavior.

As far as their temperament goes these are peaceful and calm fish. They won’t cause any trouble with other fish and rarely show signs of aggression. 

Sometimes when an iridescent shark gets scared they might dart or splash around a bit. This can be mistaken as a sign of aggression by new owners, but that’s rarely the case.

Author Note: There have been instances where these fish have gotten startled and jumped out of the tank or cracked the glass! Yet another reason to do whatever you can to keep them calm and happy.

Iridescent Shark Tank Mates

The best iridescent shark tank mates are peaceful fish of similar size. Anything much smaller might get mistaken for a snack (which you don’t want).

Since these are peaceful and shy fish any aggressive fish are to be avoided as well. Iridescent sharks don’t have the gumption to fight back or defend themselves which can make them easy targets. This is obviously less of an issue with small aggressive fish, but it’s still worth avoiding.

Some great iridescent shark tank mates are:

If you can find others that fit within the general tank mate guidelines we recommend that should be fine as well. Always introduce new fish with caution and monitor how they interact for the first couple of weeks to be sure it’s a good fit.

The Importance Of A School

Since these are schooling fish the best iridescent catfish, are more iridescent catfish. We recommend a school of at least 4 to ensure they’re comfortable.

These fish will live in a constant state of stress and worry if they’re alone. Even though it might allow you to get away with a smaller tank, keeping them alone is unfair to the fish. Our motto is to do things the right way or not at all.


If you’re ambitious and want to breed iridescent sharks, pump your brakes. These fish need very specific conditions in order to breed and they can only be found in the wild.

The sheer amount of space they need is enough to stop your breeding efforts before they start. In their natural habitat they seek out massive bodies of water before breeding, which is something you simply can’t replicate in a home aquarium.

As migratory fish, they also need to go through this process and cover distance before they consider breeding. If they haven’t migrated it doesn’t click in their brain that breeding can be an option. Again, this is something you can’t fake or replicate in a home tank.


Iridescent sharks are very rewarding and fun to own. If you’re someone who’s not deterred by large tanks and massive fish, this will be a great choice for you.

They’re also not as difficult to care for as you might think. In fact, iridescent shark care is 90% about providing them with enough space to feel comfortable. The other things like water parameters, tank mates, and food are fairly straightforward.

Since not as many aquarists want to keep fish this large (or simply don’t have the room for it) we’re always excited to hear from people who own these fish. If you’re an owner and have any fun stories or advice you think our readers should know, don’t hesitate to share!

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