Iridescent shark: Lifespan, size, breeding and tank size

Iridescent shark are a type of catfish species native to Southeast Asia and Thailand, also known as the siamese shark or sutchi catfish.

On its own, the word ‘shark’ suffices to send chills down the spine of people. The fear of this great predatory fish on the iridescent shark is somewhat lost, just like the red tail sharks. 

They provide lots of schooling activity in the aquarium. They are favored for their appearance and behaviour. 

If you are considering keeping this pet, you can should considering reading this article


Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Siluriformes
Family: Pangasiidae
Genus: Pangasianodon
P. hypophthalmus
Binomial name
Pangasianodon hypophthalmus


They are scientifically known as Pangasianodon hypophthalmus, and share a family with the Mekong Giant Catfish (one of the world’s largest freshwater fishes). 

The iridescent shark can grow to four feet as a mature adult. Being tiny teenagers, many people will buy them and not know how large they can be. 

Finding the right size tank is the greatest obstacle when holding those fish. While a 100 gallon will be ok for juveniles, it will take 300 gallons as they start growing. 

Their dazzling bright colors made them popular in the aquarium trade. They are hardy fish and eat a vast array of food.

Iridescent shark Behavior

Iridescent sharks are rather timid and can be easily frightened. When that happens, they can hit the glass or decor on their heads. 

By placing the tank in a fairly quiet area you can help keep them calm, somewhere they are not likely to be afraid of loud noises or people passing by the tank. 

They might also get harassed by more aggressive fish. Hence it is important to keep them with large, peaceful fish.

Emphasis is placed on large because any fish that can fit into the mouth of the shark will likely become food. 

They are schooling together as juveniles and separate as adults. Combined with the flashing skin, this schooling is yet another reason they have been brought into the aquarium trade.


Image by Melanochromis  from commons wikipedia

Those fish are iridescent, as the name states. As juveniles they have bright skin on their sides. They also have two stripes of black on and beneath their lateral line.

This line is a sensory organ filled with nervous tissue, used to detect water changes which is present inside this fish. 

However, once they reach adulthood, they start graying uniformly. Another trait you might have noticed for adults now is their size. 

Females tend to be larger and more ‘plumper’ than males. 

The fact that they are “naked catfish” is one unique thing about these fish, meaning they don’t have bony plates over their bodies.

They do have skin however and then choose to live in the middle of the column of water.

They have long, barbels-like whiskers, which help them feel the environment. 

There are a lot of sensory organs in fish like this and the reason for this is due to the quality of the water that they are used to in the wild.

Waters may be turbid, so that they can’t use their eyes all the time.

Habitat and Aquarium setup

These fish are native to Thailand, and thrive in deep rivers. Those deep waters allow the formation of large groups of adults. They remain in the middle of the water column, looking for food. 

They come from an incredibly diverse area (the Mekong River) that has direct impacts on both fish and people. 

The barbels on the head help them find food. This adaptation allows them to feel their way around in low visibility and water where there is a great deal of sediment or low light. 

These fish, speaking of light, are not like most catfish which are active at night; they are active during the day.

They are migratory fish too. They swim upstream for spawning during the rainy season, only to return to the lower waters to rear their young.

Iridescent shark fish Tank condition

Using this information, a river-modeled fish tank is best for those fish. This means having an open swimming space around the tank floor, with rocks and driftwood it will also help the fish to . 

The open middle water column is the essential part of the tank setup. This is where your fish will spend most of their time and need plenty of space. 

Make sure the water parameters don’t fluctuate so much to keep those fish stress free. As with most fish, even though they are hardy, they do not respond well to changes in those conditions. 

Iridescent catfish require conditions such as: 

  • Temperature: 72-79 ° F
  • pH 6.5–7.5
  • Hardness: 2-20 dGH
  • Moving water: Moderate
  • Light levels: Moderate

These fish have delicate barbels so they need a soft substrate. This will also replicate the wild conditions of the river that they are used to, which usually have a soft muddy bed. 

It is important to think about the large size of this fish and its nature. When they get scared, they can bash and break them into equipment like heaters.

To stop this, ensure that you keep your tank in a quiet area of your home. 

Consider also hiding heaters where they can’t be broken, either using an external in-line heater or a heater under gravel. 

To help keep the tank water clean, you’ll need a powerful filter because those fish are very messy.

Iridescent shark Tank mates

The biggest thing to remember when you put those fish together with others is their size. Any fish that fits into your mouth will likely end up being enjoyed as a meal. 

This means that fish such as Tetras, Danios and Barbs are not good associates. 

These are few Fishes you can include

  • Plecostomus
  • Synodontis catfish
  • Pearsei
  • Silver dollars
  • Kissing gourami
  • Leptobotia elongata loach
  • Oscar fish
  • Texas cichlid
  • Salvin’s cichlid
  • Bichir
  • Fire eel

Any crustaceans are not going to do well with these fish and are likely to end up dining. 

As always, be sure to watch them interact when adding more aggressive fish. 

Then remove the aggressor from the tank if you ever have issues. Most shops will take back fish for credit.

This will keep your tank healthy, and make sure that you don’t just waste money trying out new fish. 

You might want to check out this article Rainbow shark: Size, breeding, feeding and tank mates

Keeping together Iridescent Sharks

Young people work best in groups, and should be maintained together. Having about 4 or 5 in your tank will ensure they thrive.

Iridescent shark feeding

The iridescent shark is an omnivore, eating whatever they can find. 

They tend to eat more and more live and meaty foods as juveniles; but as adults they tend to become more vegetarian and even lose their teeth.

This behavior is shared in other fish such as Pacu, too. 

This means your work in the aquarium is a little easier. They need a balanced diet but will eat a variety of foods that are alive, frozen or pellet/flake. 

Fed your iridescent high-quality catfish flakes two or three times a day to ensure their diet is balanced.

Make sure they don’t overfeed them just by giving them enough food so they can eat it all in about 5 minutes.

Then feed them with live or frozen Blood-worms or Shrimp Brine. Do this every two or three days, instead of the flakes. This will help to give them a different source of protein they need. 

Live feeder fish, crickets and worms are another great supplement for those fish. Live fish and other live foods are a great way to get your fish nutrients as well as exit feeding and bring out their natural hunting behaviors. 

If you decide to use feeder fish, you should buy them from your local store and quarantine them for a few days in a separate tank.

This allows you to verify that they are all healthy and will not introduce diseases into your tank. 

Iridescent Shark Care Guide

The water needs to be as clean as possible to ensure your fish is happy and healthy. Iridescent catfish are inherently messy, and require a strong filter. 

By changing 25 per cent of the water a week, you can help with the filtration. This is one of the most time-consuming responsibilities to care for your iridescent sharks.

It’s important to understand how much time you need to put into a tank. Because of the size, a tank like this will take more time but it’s worth it. 

When making changes to water make sure that you carry them out slowly so that you don’t scare the fish and cause them to get stressed.

These catfish are susceptible to skin fungus and Ich as far as illness is concerned. It is more difficult to treat catfish with Ich than most other fish, since it is scaleless.

Here is an article on Red Empress cichlid: Lifespan, feeding, baby, growth & size

All over your fish, you’ll see white dots and they’ll rub their sides onto the tank. 

Medicines are available to help cure myself and my fungus; many will claim to use the dosage for scaleless fish at half strength. 

Always try to get to the root of the cause as well as medicating them-it is quite possible that if they get diseases, their water quality is not great.

Iridescent shark Breeding

Those fish can not be bred in captivity due to their size and migratory behavior. In the wild, when the water levels rise, they will travel upstream to raise during the late summer months. 

In Southeast Asia they breed in huge ponds. This allows the spawning of these huge adults without lacking the room they need. 

In captivity, the conditions required to replicate the natural breeding season are almost impossible to replicate. 

In domestic aquariums, migration alone is one aspect that is vital to these fishes and not possible. 

Because they are so hard to raise in captivity, it makes conserving their wild habitat more important.

Check out this article on Flowerhorn fish: Food, lifespan, care, types and tank size

Iridescent shark tank size

At least a 100 gallon aquarium will be needed for a juvenile iridescent shark. They’ll need a 300-gallon tank as adults. 

As juveniles they will thrive in groups of approximately 4 or 5. This schooling will enable them to swim less fearfully in the water column.

You should allow another 150 gallons for each iridescent shark which you add after 300 gallons for the first fish.

How was the fish named?

The name of the fish is given for the glow or iridescence in juveniles, as well as the shark-like appearance of this and other shark catfishes.


This type of shark fish Adults reach lengths up to 130 cm (4.3 ft) and can weigh up to 44.0 kg (97.0 lb) at most.

They have a bright, iridescent color that gives their name to these fish.

Big adults are uniformly grey, however. The fins of iridescent shark fish are black or dark gray. Juveniles have a lateral black stripe, and a second black stripe below the lateral line.

Distribution and Habitat

Iridescent sharks originate in Asia from the great rivers Chao Phraya and Mekong, although they were introduced for aquaculture in other rivers.

They prefer large bodies of water similar to that of their native Mekong river basin’s deep waters.

The iridescent shark is a migratory fish that moves upstream in most regions to spawn during the flood season while the waters are high and return downstream to seek habitats for rearing when the river water levels fall. The migration dates vary according to the river system.

They migrate upstream in the Mekong river basin from May to July and return downstream during September through December.

South of the Khone Falls, upstream migration occurs at the end of the flood season in October to February, with its peak in November to December; here, it seems to be triggered by receding waters.

An environmental group in Santander, Colombia, confirmed in August 2015 that iridescent sharks have been found in one of the tributaries that feed into the Magdalena River, having accidentally been introduced from the area’s illegal farm fisheries.

The finding has given rise to alarm among the scientific community and government officials, as the Magdalena River is home to over 200 native species of fish, 35 of which are at risk.

In aquarium

While juvenile iridescent sharks are being sold for home aquariums as pets, it is not an easy fish to keep.

While they can survive in a 40-gallon aquarium, iridescent sharks are schooling fish that prefer groups, are used to living in rivers, and are space-needing active fish.

They have very poor eyesight so mobility can be seen as a threat from outside their habitat.

When stressed their first instinct is to flee; in an aquarium environment, a blind dash can cause injury.

These injuries can cause the fish to sink to the bottom, where it can lie on either side or back until it recovers.

To develop naturally, the iridescent sharks require a minimum tank size of 12 m (39 ft). Schools need tanks which are even larger.

They can reach 1 m (3.3 ft ) in length when given enough room and fed adequately.

The lack of space at most home aquariums stunts their growth. That is why most iridescent sharks kept in the home aquarium only grow to lengths of 15 to 30 cm (6 to 12 in) and may die prematurely.

If adequately sized aquarium and proper husbandry are provided, iridescent sharks can live in their adolescents and grow to full size.

History of Iridescent shark

The iridescent shark fish (Pangasianodon hypophthalmus) is a shark catfish species (family Pangasiidae) native to South East Asian rivers. It is not a shark, despite its name.

It is found in both the Mekong basin and the Chao Phraya River, and is heavily grown there for food. 

The meat is frequently marketed under the common Swai name. It was also introduced as a food source in other river basins, and its striking appearance and iridescence made it popular among fish keeping hobbyists, among whom it is also known as the Siamese shark or sutchi catfish.

The omnivorous diet of the Swai is composed of crustaceans, other fish and plant matter.

Do Iridescent Sharks fit for your Aquarium? 

Concluding Thoughts

You should know the key care points regarding this fish after reading this guide; they are large and it will take a lot of time to keep their tanks clean. 

Their size makes them truly difficult to maintain. Having a tank which is large enough to keep an adult fully grown is something that only a few people can afford.

Youths are smaller and will fit in smaller tanks, but you still need to be prepared for this growth. 

When it comes to water conditions, they are really hardy fish, and fit perfectly with other bigger fish. 

It’s easy to feed these fish, because they’re going to eat anything that fits in their mouths; just keep it varied.

Pangasius has no gourmet reputation and is sold cheaply in the United States as Swai, panga (or pangas) in Europe, and in several Asian countries as cream dory and basa. 

Despite its poor reputation, Vietnam ‘s total export of pangasius stood at US$ 1.8 billion in 2014. 

Because of their low cost, slight taste and firm texture, pangasius fillets are an increasingly popular product.

Pangasius is an omnivorous fish and therefore does not require in its diet a high level of animal protein. Typical sizes for grading are 3–5 oz, 5–7 oz and 7–9 oz.

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