Iridescent Shark: The Definitive Care Guide

Iridescent Shark: The Definitive Care Guide

Knowing what to expect is important before you bring any fish (and especially catfish) into a tank, and iridescent sharks need additional consideration. They can live for up to 20 years, which is a very long time for a fish, so make sure you will be able to provide it with adequate iridescent shark care for as long as it lives before you invest time, effort, and money in this peaceful fish. When these impressive animals are kept alone in a tank, it is not unusual for them to experience stress and anxiety, and a considerate aquarium owner should always strive to keep more than one iridescent shark or to provide appropriate tank mates.


The iridescent shark pangasianodon inhabits the Chao Phraya River and the Mekong basin, and in these areas, this large fish is often used for its meat as food. The name “Swai” is what the meat of iridescent sharks tends to be sold as, and it is considered a delicacy in many areas. In recent years, the Pangasianodon hypophthalmus has grown in popularity as an aquarium fish, and it can now be found in aquariums all over the world.

The name can seem a little confusing due to it being a catfish and not a shark, but there is actually a logical explanation behind it. It physically resembles a shark, despite being a fish, and the name is also inspired by the way juvenile sutchi catfish glowing body. Measures are being taken to make sure that the iridescent shark continues to thrive in the wild, due to their unique breeding behaviors, but it has also become a popular aquarium species for those who have the space and the time to dedicate to caring for it.


Catfish usually have their body covered in bony plates, but this siamese shark is different from other similar fish and is sometimes referred to as a naked catfish. They are eye-catching and iridescent – more so when they are juveniles, and below the lateral line, you will find two black stripes running parallel. This is unique for the juveniles and a great way to determine a fish’s age, and they become increasingly more grey as they grow older. The fins are black or dark grey. The lines on their bodies are more than just a nice visual detail, and they have nervous tissue that becomes beneficial for the siamese shark when wanting to detect water changes. The reason isn’t that they have poor eyesight, but instead that they often swim in murky waters.

The female siamese shark is often slightly larger than the male, and the shape of their bodies tends to have more volume to it – making female fish easy to distinguish, which is especially great for when wanting to breed iridescent sharks. Iridescent sharks also have long barbels that resemble whiskers, which is more of a typical feature found in most fish of this type. Their barbels are characteristic and give them an interesting look, and it is hard to mistake this fish for any other species.


What you need to know about a fish like this is that it is generally peaceful and calm, but it does scare easily which can cause it to move around for a moment or two. Some inexperienced aquarium keepers may be lead to believe that this is a sign of the fish being aggressive, but aggression in sutchi catfish is considered unusual. Knowing how skittish they are though, having a tank of good size is essential, as it needs space to swim. Sutchi catfish are large and surprisingly powerful, and if they get frightened it is not unheard of for them to break the glass or even jump right out of the tank, and with this in mind, you should always try to avoid scaring them if possible.

Other than that, iridescent sharks are easy-going and friendly, they get along well with other fish of a similar size and they mostly need sufficient space, the right tank water conditions, and proper iridescent shark care. When you provide everything they need, you get to see a confident and interesting fish – one that seems to have its own strong personality and quirks, and many of those who own fish like this confirm that their personalities can be larger than life itself.

These fish do better when provided with other fish for company (see more about tank mates below), and while they can be kept alone, you will quickly notice how much more confident, outgoing and curious they seem to be when swimming around with friends. Iridescent sharks are very social and it is recommended that you do not attempt to keep them on their own, isolated from others. An unhappy fish will likely have a shorter life, but if cared for properly – the iridescent shark pangasianodon hypophthalmus can live for up to 20 years.

Tank Conditions

An iridescent shark needs a nice and large tank to swim around in, and you will want to give these fish a tank with at least 300 gallons. This should make it clear that the siamese shark is not made for regular small aquariums, so consider the size of the tank and whether you have space for one before you proceed. The recommended 300 gallons is also only for one fish, and you should count on adding an extra 150 gallons per additional fish, which quickly adds up. The challenge in caring for an iridescent shark lies mostly in the amount of space it needs.

Once you have a suitable tank, it is time to set it up. Being a hardy fish, the iridescent shark can often survive in variation conditions, but they prefer water with pH 6 to 8 (with pH 6 being slightly low and pH 8 somewhat high), 2 to 20 dGH hardness, for the water to have a minimum temperature 72 -79 degrees Fahrenheit and for the aquarium conditions to resemble their natural habitat.

Being as large as the iridescent sharks are, you might even want to consider keeping them in a pond instead of in an aquarium (however, this requires additional knowledge and precaution), but if you do choose to keep them in a tank – it cannot be stretched enough how important it is to get one that is big enough to give them the freedom to swim around. As mentioned above, an iridescent shark does not like to be alone, and for every fish you add, you need more space and more water.

Plants and vegetation

When it comes to plants, this is actually of less importance for the iridescent shark! Their natural habitats are shallow parts of rivers, so what you should focus on is providing the fish with a good material for the bottom of the tank, driftwood and some large rocks as this helps mimic how the iridescent shark lives and thrives in the wild. A few plants is always a good idea as it can help improve the water quality, but even if you may feel it will look pretty to cover the bottom of the shark fish tank with a variety of plants – your iridescent shark will benefit very little from it. The same goes for placing larger plants that reach up to the surface or that float on the surface, as these will mostly take up space and limit the iridescent shark’s space to swim.

A good compromise is to add a few carefully chosen plants to the tank but to not overdo it as these are not fish that require hiding places thick vegetation. For those who dream of keeping an aquarium with plenty of green – an iridescent shark might not be the right option for you.

Maintenance and Care

The iridescent shark can be quite the little mess-maker, and they tend to get their tank dirty fast. For this reason, you need to make sure you have a strong filter, and that you are also cleaning the water regularly, as these fish (despite being messy themselves) do not thrive in dirty water. Many experts recommend changing approximately 25% of the water in the tank every week, something that will inevitably be time-consuming considering the large tanks fish like these need. Knowing what you sign up for when getting iridescent sharks for fish tanks is crucial in order to succeed, as you might end up keeping them for up to 20 years.

Be gentle and careful when changing the water and cleaning the tank, because as we have already talked about above – the iridescent shark scares easily, which could end up damaging your tank or even harming your fish. You should also keep the tank in a calm area of your home if possible, with minimal disturbance. These are fish that look very large and impressive, but they can end up hurting themselves quite severely if spooked. If they were to jump out of the tank when you are not present, then your fish is likely to die, so make sure you provide a calm environment especially for when you are not around to supervise.


Iridescent shark fish are not prone to any specific illnesses and diseases, but they may be perceptive to certain skin issues if unlucky. This is usually easy to see (discolorations, etc. etc.) on their bodies and could require special treatment. Medication is available for skin conditions and fungus in these fish, but as they are scale-less, you might need to adjust the dosage.

However, the best thing you can do as an iridescent shark owner is to try and prevent this so that you never get to the point of having to treat it, and this can usually be done by simply monitoring the water quality and providing a high-quality diet. DIsease and illnesses will usually have a cause, and it is not uncommon for that cause to be environmental, meaning you are likely to be able to prevent it by taking better care of the tank.

Recommended Diet

Like most catfish, the iridescent shark prefers a diet where there is variety, so it is recommended that you provide food that will stimulate their natural desire to eat. The iridescent shark is an omnivore, which means it eats both meat-based and plant-based food. Some studies seem to show that while the iridescent shark is young, it tends to eat more meat, and then gradually move over to a more plant-based diet as they age.

The smartest choice is to feed a high-quality flake diet from a respected company, as this will make sure they get all the nutrients they need to live for up to 20 years. A lack of essential nutrients could potentially shorten the fish’s lifespan, which is why it is a good idea to provide flake food as a base. On top of that, to keep them from getting bored with the food, you will want to add a variety of extras such as brine shrimp, feeder fish, worms, and also bloodworms.

Suitable Tank Mates

When you have fish like the iridescent shark, having more than one is recommendable as these are used to living in pairs or groups in the wild, and they generally don’t do well on their own. There are good tank mates and bad tank mates, and a general recommendation is to choose tank mates of a similar size. Why is this? Because if you were to add small fish like danios, tetras, and barbs, these are likely to end up becoming dinner for the iridescent shark. Instead, consider having more than one iridescent shark, or one of the following fish breeds:

Aggressive fish should be kept an eye on to prevent one fish from bullying another, and if you notice this type of behavior in your tank, you are probably better off removing the aggressive inhabitant to restore peace and order. The iridescent shark does not enjoy the disturbance an aggressive fish might end up causing, and it could end up permanently damaging their health and well-being. Regardless of what tank mates you choose for your iridescent shark – make sure you have enough space in the tank.

Schooling the Iridescent Shark

Living alone in the water is not natural for this fish, and they can get stressed and even depressed if kept by themselves for too long. This should not be something you want for your aquarium, so it is recommended to have a school of somewhere around 4-5 iridescent shark fish in a tank in order to keep them comfortable. Other tank mates are also good options, but studies seem to show that schooling is important for the iridescent shark.


SILURE REQUIN pangasius hypophthalmus
Getting the right tank mates is one thing, but you also need to consider if you would be interested in breeding your iridescent shark. If so, you would obviously need a made and a female iridescent shark, but after that comes the bad news. The iridescent shark is considered close to impossible to breed in captivity, and this is due to the difficulties in recreating the right conditions for this to happen naturally. The iridescent shark is a migrating fish, something that means that during the breeding season (late summer), the fish will travel upstream with the rising water levels, where it will then go on to breed.

No size aquarium is big enough for this to be a possibility, and it seems that unless the iridescent shark is able to migrate, it has no interest in breeding, even if there are both male and female fish in the tank. It is irrelevant what size your aquarium is, as not even the biggest size available is likely to inspire your iridescent shark to want to breed.

As this species cannot be bred in captivity, it is incredibly important for them to be preserved in their natural habitat, and that they are allowed to continue migrating and breeding there. So, if you had the hopes of breeding your iridescent shark somewhere down the line, then you are unfortunately up for some disappointment.

FAQ (Frequently Asked Questions)

1. Will iredescent sharks eat fish?

Yes. This fish is an omnivore and eats both animal-based and plant-based food, and they will happily eat small fish despite not being an aggressive fish.

2. Do iredescent sharks play dead?

Sometimes, and especially when scared, this is a fish that might choose to play dead. If your fish is floating around in the water, double-check to make sure it isn’t just pretending before removing it from the water.

3. How big do iridescent sharks get?

Expect an adult size of up to 4 feet.

4. Are iridescent sharks aggressive?

These large fish are not usually considered an aggressive type of fish, and they tend to live peacefully also when kept in a tank with other fish. It is always good to be vigilant, however, especially if you have just introduced a new fish to the tank, and to consider rehoming any fish that is displaying repeated aggressive behavior.

5. How do you take care of an iridescent shark?

As long as you have a generously sized tank that can provide your fish with adequate space, water with the temperature 72 to 79 degrees (F), water pH 6 and up, your iridescent shark only requires quality food and nutrition, a clean tank and appropriate tank mates.

6. Are iridescent sharks nocturnal?

Catfish are known for being nocturnal, but the iridescent shark is an exception! It tends to be the most active during the day, and it is generally found to be completely inactive at nighttime.


There is definitely some work that comes with having iridescent sharks in your tank, but the biggest challenge is to provide them with a big enough tank – the right size for them to swim around and thrive. Yes, it is considered a fish for the experienced aquarium owner, but most of this has to do with space, and how far from everyone is able to provide properly for such a large animal. If you are able to provide an aquarium the size they need, then you are likely to find great joy in having this fun catfish swimming around.

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