Iridescent Shark: Care, Diet, Tank Size, Tank Mates and More

A fairly young Iridescent shark

The Iridescent Shark is a very popular freshwater fish and also one of the least kept aquarium fish. The reason behind its popularity is that it packs so many desirable qualities.

First of all, its appearance. The thing is, lots of hobbyists get intrigued just by the thought of having a shark-like fish in their tank.  Especially if they don’t have to deal with the fear that comes with keeping the real one.

The Iridescent shark is quite peaceful unlike other freshwater aquarium sharks like the Rainbow Shark. This makes it possible for them to be housed with so many other tank mates.

Regardless of their size, their care is rather straight forward and easy due to their hardiness and non-picky eating behavior.

They only became one of the least kept fish because of the size of the aquarium they need.

Even though they are very popular, many hobbyists don’t know much about them. Unfortunately, many decide to keep them without fully understanding their requirements.

As a result of this, many iridescent sharks are victims of improper housing.

This is why I prepared this guide to provide you with all you need to know about keeping the Iridescent shark from tank size, water parameters, diet, tank mates and much more. 

By the time you are don’t reading it, you will have all the information you need to keep them successfully, and you will be able to decide whether its right for you or not.

Let’s get to it!

Also known as Siamese Shark or the Sutchi Catfish, the Iridescent Shark (Pangasianodon hypophthalmus) is from the same family as the well known Mekong Giant Catfish. The family is referred to as Pangasiidae and comprised of the shark catfish. Other less known members of this family include Pangasius, Basa and Helicophagus. 

Despite having the word “shark” in their name, the Iridescent shark share nothing with the actual marine shark. Well! Apart from their physical appearance obviously. 

These fish earned the word “shark” in their name because of how closely they resemble the real shark. They earned the word “iridescent” because of the glowy nature of their body, especially when juvenile.

The iridescent shark is native to Thailand but can now be found throughout Southeast Asia. You will find the highest concentration of these fish in Chao and Mekong rivers which are two of the largest rivers in Southeast Asia. 

These tropical freshwater fish prefer sticking to those rivers because they are sufficiently deep and wide for them to ramble around easily. 

This is why they do better in deep waters. Plus, since they are migratory fish, those large rivers will allow them to travel far to where the conditions suit their need. 

Normally, they move to deep waters during rainy season to spawn and relocate to lower water to rise their young.

Because of their size and availability, the Siamese Shark is also used as food by people dwelling near the Mekong and Chao rivers. Many people in those areas consider it as a delicacy. They are sold under the name “Swai”

While they may not look like most catfish they still have a very obvious feature that gives all catfish away- barbles. 

The barbels are adaptive features that help them understand their surroundings in areas with low visibility. Examples, places where the water is murky or areas where light cannot penetrate well due to vegetation.   

Contrary to most catfish, the iridescent Sharks aren’t nocturnal. This means that they aren’t just active at night, they are active during the day as well.  

Iridescent Shark Care Snippet

  • Maximum fish size: 4 feet
  • Minimum tank size: 300 gallons
  • Aquarist Experience Level: Expert
  • Temperament: Peaceful
  • Temperature: 72°F to 79°F
  • PH: 6.5 to 7.5
  • Hardness: 2-20dGH
  • Diet: Carnivores
  • Care Level: Advanced
  • Ideal tank mates: Oscar, Birchir, Salvini Cichlid, Silver Dollar, Plecostomus Kissing Gourami, Tinfoil Barb, et Cetra.


Thanks to their name, the iridescent shark appearance isn’t so difficult to imagine. 

You probably need to just know that they are catfish to put everything together. Combining the physique of sharks and some catfish features give them an almost unrivalled and very unique appearance.

Like most sharks, they have a very prominent dorsal fin which sure looks like a sail. The dorsal fin looks even more awesome when the shark is swimming and it spreads or curls back depending on the direction of the swim.

They have a very large caudal fin and resembles the dorsal fin in both color and the sail-like appearance. Their anal fin starts close to the belly and ends on the caudal peduncle.

Their eyes may seem large when juveniles but will grow into it when they mature. 

The iridescent shark is sometimes called a naked catfish. That is because unlike most catfish their body is not covered in bony plates, it is just covered in skin. 

Iridescent Shark Appearance

Their skin contains some visible lateral lines which are nervous tissues and help them detect their surroundings more effectively. 

Their barbels also help them navigate the environment easier. That is not to say these fish have poor eyesight. 

It’s just that sometimes the waters may be murky which can hinder visibility in which case the eyes won’t help that much. 

Juvenile iridescent shark are covered in a shimmering dark skin. As they start to mature the skin shimmers less and start turning grey.

Two major differences between male and female Iridescent shark are that females are usually bigger and rounder than the males. 

An albino Siamese Shark


Size is what deny many hobbyists from keeping the beloved Iridescent shark. 

They are undoubtfully one of the largest freshwater aquarium fish, way bigger than the freshwater Bala shark which itself is remarkably large.

On average, the iridescent shark will grow to a maximum size of 3 to 4 feet. Surprisingly, many aquarists buy these fish without having an idea on how large they can get. 

This is why many iridescent sharks are victims of improper housing, being stuffed in tanks that isn’t adequate for them.

There are also many cases where owners had to give them away because they can’t provide a suitably sized tank.

Given how long they live and how large they can get, its important to make sure you can supply them with all they need throughout their lives before getting one. 

It doesn’t need to be said that it isn’t fair to provide them with anything less than ideal. 

Iridescent Shark Lifespan

Almost everything about these fish is grand and that include their lifespan. In ideal condition and with proper care, the lifespan of an Iridescent shark is around 20 years. 

They are one of the very few freshwater species that can live this long which means keeping them is no small commitment. 

Factors such as water quality, poor diet and unsuitably sized tank can significantly lower their lifespan however.

Temperament and General Behavior

Regardless of what their size might suggest, the Iridescent sharks are very peaceful and get along well with species within their size range. 

When you consider their size it’s hard to agree that they also get startled easily. Sutchi Catfish are naturally shy and nervous, and get spooked easily. 

As their owner, you should do whatever you can to prevent them from getting scared or at least lower the occurrences. 

You can achieve that by keeping their tank in a reasonably quiet area, hopefully where people rarely pass. That’s because when they get scared they may run into the wall of your tank which can create a problem due to their enormous size. 

There have even been some cases where they broke the tanks glasses or jump straight out the tank.

Sometimes when they get scared they act by splashing and darting around. This can easily be mistaken for a sign of aggression by people who don’t have much experience with them. The truth is, Iridescent Shark very hardly show any sign of aggression. 

In terms of swimming pattern they spend most of their time roaming in the middle section of the water. They aren’t bottom dwellers like most catfish.

It’s important to point out that Iridescent shark do way better when kept in groups and the reason is they are schooling fish.

They feel safer, more confident and less stressed when among their kind. This will in turn make them healthier and have a higher lifespan potential. 

Taking all these in to account I highly recommend you avoid keeping a single Iridescent shark in your tank.

A fairly young Iridescent shark

Iridescent Shark Tank Size

Owing to their size and activity level, the Iridescent Shark isn’t cut out for your usual home aquariums. You will need a minimum of 100 gallons for a juvenile Iridescent Shark and a minimum of 300 gallons for an adult. 

Putting them in tanks smaller than these will be a terrible idea because they won’t have the needed space to swim around easily. This, without question, will affect their well being and overall lifespan. 

Even people feel somehow immediately they are cramp in a small space, its not different for a fish.

Since keeping only one is not recommended you should add additional 150 gallons per fish on top of the 300-gallons.

It’s alright if you decide to start with a smaller tank when they are juveniles like some owners do before switching to a bigger one. Just make sure you make the switch before the fish desperately need it. 

Tank Requirements

The next thing to do after selecting a suitably sized tank is fashion it so that it closely resembles what they are used to in the wild. 

Let’s start with the substrate. The obvious choice is something soft. This is not just because their barbels are very sensitive but because a soft muddy substrate is what you will find in their habitat. 

Other elements to add that will help mimic their habitats base include pieces of rocks and driftwood. 

But don’t overdo it, they need free-roaming space more than any of that. Also, take their size into account so you can achieve the desired result.

As opposed to most aquarium fish, the Siamese Shark does not need hiding spaces in their tank. 

As such, aquarium plants do not have a special place in their tank. 

They aren’t used to plants in their natural habitat so they will just end up inconveniencing their movement in the tank. 

However, if you still want your tank to be planted you can do it lightly and use plants like Hornwort or Anacharis since they grow quickly. But know that your plants will most likely get eaten by them. 

Then there is the issue of filtration which is something you don’t want to skimp given how messy these fish are. 

They are large fish that put out a lot of waste so you have to use a very powerful filter to keep the water always clean. 

Lastly, you need to stick to performing the recommended water replacement. Many aquarists recommend replacing 25% of the water in the tank weekly. 

It’s important you carryout the process very carefully and gently to avoid spooking the fish.

Iridescent Shark Water Parameters

Although they are substantially hardy it’s still important you avoid fluctuations in their water parameters to avoid any complications.

Iridescent sharks do best when kept within the following parameters. 

  • Temperature 72°F to 79°F 
  • Water Hardness: 2 to 20dGH
  • pH: 6.5 to 7.5

You will need a heater to maintain the temperature ranges so I recommend you use an under gravel heater or even an external inline heater. The essence of using these filters is they will not be broken when the Siamese Shark get startled as opposed to the usual ones. 

Lastly, make sure to provide moderate water movement and moderate lighting.

Food and Diet

Luckily, Iridescent Shark are omnivores and eat almost anything they can find in their tank like most catfish. 

It would have been a nightmare if they only eat a particular food given their size.

What’s interesting is their feeding habit changes from when they are young to when they mature. They tend to stick to eating more of live and meaty foods as juveniles, but switch to more of plant-based food as they mature. 

Feeding the Iridescent shark in captivity isn’t as challenging as most people would expect. They readily accept all of sorts of fish foods from pellet, flake foods, live and frozen. 

Your task is mostly to ensure you make the diet as varied as possible so their body can get all the nutrients it needs.

You can use flakes/pallets to make a good portion of their diet but make sure they are high quality. 

After every 2 to 3 days you can feed them protein-enriched foods like brine shrimp or bloodworms instead of the flakes.

Its also a good idea to supply them with live foods such as feeder fish, crickets and even worms. This will make them happy seeing as they are used to hunting in the wild. Plus, live foods will help build their enormous body and keep them healthier. 

Make sure you purchase the live foods from a reputable store. And quarantine them for some time to confirm they aren’t carrying any diseases before giving your Siamese Shark.

It’s not hard to understand why some end up overfeeding their sharks when you remember their size. 

However, you should always avoid that to prevent problems in your tank. 

I recommend feeding them 2 or 3 times a day as much as they can in 4 to 5 minutes each time. 

Iridescent Shark Tank Mates

Before considering any other fish in your tank I highly recommend you have more than one Iridescent shark. 

As always, it’s important to consider size, temperament and water parameters before keeping two different species together.   

Starting with size, keeping the Sutchi catfish with small freshwater species like Rasbora, Tetras, Danios will not work because they will most likely get eaten. 

Although these sharks are huge, they will not do well with overly aggressive species like the Jack Dempsey Cichlid

Nevertheless, some owners have been able to successfully keep theirs with aggressive species. 

If you want to try it try out as well, I highly recommend you monitor your fish closely. This is so that you can remove the aggressive species from the tank when it’s stressing out your shark.

All things considered, these are some of the best Iridescent shark tank mates

  • Silver Dollars
  • Texas Cichlid 
  • Salvini Cichlid
  • Oscar Cichlid 
  • Plecostomus 
  • Synodontis Catfish
  • Pearsei 
  • Tinfoil Barb
  • Bichir
  • Kissing Gourami

In case you are introducing a fish outside of these make sure you conduct through research and stick to the recommended guidelines. 


Sadly, breeding the Iridescent shark in captivity is something that no one has been able to accomplish. 

That’s mostly due to their enormous size and migratory behavior. Remember I mentioned that they travel to areas with high water level during summertime to spawn. 

Once they don’t experience similar condition and cannot migrate they will feel that the area is unsuitable for them to spawn. And this kind of condition and space is something you won’t be able to replicate in captivity. 

Not unless you have an aquarium that runs for hundreds of meters to say the least. 

Currently, they are being bred in a very ginormous pond located in Southeast Asia. They can spawn there because the pond is big enough for them to move from one area to another. 

A fully grown Siamese Shark

Common Diseases

Iridescent Sharks do not have any species-specific diseases. Whilst this is good news it does not mean they aren’t susceptible to any diseases especially if you consider their lack of scales. 

What you need to watch out for are the most are common freshwater infections such as ich. Ich if you haven’t come across it, it’s a very popular freshwater fish disease caused by a parasite called Ichthyophthirius multifiliis

It’s most likely to affect your fish when you let your tank get dirty or the water quality drops.

Fish affected with this disease appears as if its sprinkled with salt and also make them feel itchy. 

The good news is as long as you maintain top-notch water quality, feed you fish a healthy diet and provide them with a suitably sized tank, their chances of getting sick will be significantly reduced.


Truly, the biggest challenge of keeping the Iridescent shark is providing them with a suitably sized tank and the maintenance that comes with it.

If not for this reason, I bet these sharks would have been in homes of almost every hobbyist, like the Tetras for example. Owning a shark-like catfish will never be uncool.

I hope by now you have realized that keeping them isn’t as mysterious as many people think.

Their care basically entails providing them with a suitably sized tank (I recommend you get a 300-gallon tank even if you are buying a juvenile). 

It would be better if you can keep more than one. Next, you set up the water condition to what is ideal for them and avoid parameters fluctuation as much as you can.

After that, you need to equip the tank with a soft substrate and throw in some driftwood and pieces of rocks to resemble what they are used to in the wild.

Performing a scheduled testing will help you achieve that, and replacing 25% of the water every week. 

Feeding them a high-quality varied diet is necessary if you want your fish to stay healthy. 

Should you choose to add more species to their tank make sure they aren’t overly aggressive and within their size range.

This pretty much sums of the Iridescent shark care. The routines that come with keeping the iridescent shark aren’t so challenging, their size is. 

So if you can afford to provide them with the right tank and can handle a large fish, the Iridescent shark will be an awesome choice for you.

Hopefully, this guide has helped you understood all you needed to know regarding these fish. If you are contemplating whether to keep them or not I hope it helps you make the right call.

Own an Iridescent Shark? I will appreciate if you share any experience you think can benefit this guide.

You May Also Like!

Leave a Comment

Your email address will not be published. Required fields are marked *