IRIDESCENT SHARK CATFISH - Description and Aquarium Care

IRIDESCENT SHARK CATFISH – Description and Aquarium Care

Iridescent Shark, judging by its name is an attractive fish that has many common names such as Pangasius Catfish, Siamese Shark, and Sutchi Catfish.

These fish originate from Southeast Asia like Thailand, the Chao Phraya River, and also in Mekong Basin. Its name Iridescent Shark is a result of its shark-like appearance.

Iridescent shark catfish belong to the family of Pangasiidae and also of the species of Pangasianodon hypophthalmus.

Background/Distribution and Conservation

Pangasianodon hypophthalmus is found as a juvenile in a large number of schools mostly in stretches of rapids. But, they tend to isolate themselves as an adult.

They are native to Asian rivers. And, are common in large rivers and streams. Iridescent shark catfish are available as a staple food in Southeast Asian countries such as Laos and Thailand. Also, they are quite popular in the aquarium trade.

They are available as important fish in aquaculture and they have several variations like albino pangasius catfish or Albino Iridescent Shark.

On IUCN Red List, they are listed as “Endangered” species due to known threats causing a decrease in their natural population.

Major threats contributing to the decrease of this fish species include Biological resource use – Fishing and harvesting of fish for the aquarium trade, Natural system modifications – Dams and water management/use, Pollution – Agricultural and forestry effluents.

Iridescent shark is a migratory fish that move upstream to breed during the season of the flood. That is when waters are high.

Afterward, they return back to downstream to seek rearing habitats when the water levels are back to normal. The dates of the migration are usually between May to July.

Iridescent Shark catfish Identification

This awesome fish can be identified with its shiny, iridescent color that differentiates it from most other fishes. Usually, Iridescent sharks are either black or grey. Thus, most of the adult iridescent fish are grey while their juveniles usually have a black stripe on the lateral line and another black stripe underneath the lateral line.

This lateral line is a sensory organ that this shark species use in detecting changes in the water. The Iridescent Shark has a body shape that resembles that of marine shark. More so, like every other catfish, they possess two pairs of maxillary barbels at the corner of the mouth.

The shark’s adipose is well developed, usually on the underside with a long anal fin that extends from the flat belly part to the bottom of the caudal peduncle (tail fin).

Iridescent shark has a short dorsal fin with a strong spine (usually 1 or 2) on its pectoral fins. Pangasius Catfish, as an adult are generally darker and lack the usual stripping compared to when in the juvenile stage. Although, they still retain the glow that gives them their name.

The abdomen of an Iridescent Shark and its mouth are silvery in color. Their eyes and head are big just like every other catfish. And, the unique thing about them is the fact that they are “naked catfish” which means they do not have bony plates on their body.

Nevertheless, they do have skin and also live in middle water. Another thing is the fact that their dorsal fin has a shape like a sail and will tuck back or fan out depending on how they are swimming.


Fishes like Iridescent catfish has a lot of sensory organs. This is to augment their poor eyesight which may cause them not to use their eyes most times. Especially, when the water is murky. As such, they depend mostly on their sensory organ.

These fish also has an albino which is very rare in some part of the world. However, the only difference with the albino and the regular iridescent shark is that their body is all white and they have red eyes.

Typical Behavior

The iridescent shark is skittish and nervous by nature. As a result, they do well in a calm living environment where people are unlikely to scare them through sudden movement around their tank or loud noises. Unexpected noise may cause them to injure themselves.

When Iridescent Sharks are small, they do well in school. However, as they grow older they tend to keep to themselves.

This species of freshwater shark do not bother other tank mates when in juvenile. But, they might eat small fishes in the aquarium as they grow older.

These beautiful fishes are large, active swimmers and most times would outgrow their tanks if it is not large enough. Therefore, if you have bought this fish and you are keeping it in a small tank, please reconsider your decision. Either you return it to the store or go get a better bigger tank.

Venomous: They do not have any venom

Interesting Facts about the Iridescent Shark Catfish

  • Iridescent Shark catfish do not have bony plates on their body. Hence, the reason it is known as naked fish
  • The majority of sharks including iridescent shark has cold blood in their bodies.
  • A female shark can get pregnant through multiple male partners
  • Iridescent shark do not sleep

Iridescent Shark’s Compatibility with Other Tankmates

These fishes do well with their species when in the juvenile stage. As such, they would not thrive without being in a school of about 4-6 of their species.

Iridescent shark is by nature a peaceful fish species. Therefore, it makes a good community fish.

While keeping them with other large peaceful fish do not add small fishes or other animals like tetras, barbs, danios, snails, and crabs to the tank as they may end up serving as their Breakfast.

They will mostly make good tankmates with other large fishes such as pearsei, plecos, silver dollars synodontis catfish, kissing gourami, leptobotia elongata loach, Oscar, Texas cichlid, and Fire eel.

On the other hand, take caution when adding fish like peacock bass, Redtail shark, Molly fish, Piranha, Silver Arowana, and Barbs. These fishes may be territorial and scare the Iridescent sharks easily which may lead to stress or injuries in fish.

Feeding and Foods

Iridescent Shark Catfish are omnivores by nature, therefore, they would eat both plants and animal food matter. They consume practically anything they can find in the tank.

The iridescent shark is popular for its huge appetite. And as they are growing, they consume more meaty and live foods. When kept in the home aquarium they eat all kinds of fresh, live, flake and pellets food.

As Juvenile, they require a tangible amount of protein in their diet for them to grow at a fast rate. However, the Iridescent Shark will do better with mixed feeding. Thus, combine veggies and meat to ensure they are getting the balanced diet they require.

As adults, they tend to lose their teeth and become more vegetarian. Ensure to feed them two or three times a day with a portion that can last up to 4-5 minutes.

When feeding them with a protein food, feed them with bloodworms, prawns, small fishes, crickets, and worms or brine shrimp. Another important supplement that you may need to add to their feeding is live feeder fish.

Giving them live fish is a way to bring out their natural hunting behavior. Hence, when you decide to feed them with feeder fish, get them from a local store and then ensure they are quarantined before you add them to your aquarium. For plant foods, give them lettuce leaves, squash, cucumbers.


When you take a closer look at your iridescent sharks, you will realize that the females tend to be a bit larger than the males. Also, they tend to have a lighter color.

Iridescent Sharks’ Life span and growth rate

One of the biggest problems aquarists have with these fish is that they grow up to be a very large fish that is difficult to keep in a home aquarium.

Most times, the Iridescent fish always get purchased by people who do not really know much about them which may lead to fish suffering from proper care and the owners having to give them away.

These awesome fishes can grow up to 47 inches (120cm) maximum in total length if taken care of properly. They also have a great life span and can live up to about 20 years if you provide them with the right tank requirements.


If you are excited about breeding iridescent fish on your own, sorry to burst your bubbles. But, breeding this kind of fish is very rare in a home aquarium due to how large they get and the requirement for the spawning.

In the wild, they make use of large water bodies. And, the breeding and mating occur in late spring or early weeks of summer.

Iridescent shark is comfortable laying their eggs in the middle of streams and ponds. This is something you cannot replicate in an aquarium setting.

Being a migratory fish, iridescent catfish need to have to migrate to their spawning grounds before considering breeding. Hence, if they do not migrate, it does not register in their brain to breed and it is something that cannot be faked in a home aquarium. Most Iridescent fish you find in the market are bred in huge ponds of Asian fish hatcheries.

Iridescent Shark swimming upside down

If you suddenly wake up to your iridescent shark catfish swimming upside down, it means it has a problem with buoyancy. As such, you need to react immediately and start treatment on time.

The usual cause of impaired buoyancy is a malfunction in the shark’s swim bladder. Thus, when your fish gets affected by swim bladder disorder, it often loses the ability to swim properly.

Therefore, it will float uncontrollably to the aquarium top, turned upside down and not dead. In a few cases, the iridescent shark will lay sideways on the bottom unable to swim to the top.

Your shark will get swim bladder infection as a result of pressure from a bloated belly. In other words, too much air swallows and bacterial infection.

Iridescent Shark not eating

There are two reasons why your iridescent shark may not be eating. Either it is sick or does not like the food you are feeding it.

Above all, it is very rare for iridescent shark not to eat. In cases like that, consider changing their diet entirely to live foods such as blood worms.

Aquarium Care Sheet for Iridescent Shark Catfish

In a Glance

  • Max. Size: 47 inches.
  • Size of Tank Required: 400 gallons and above.
  • Suitable Tankmates: Oscars, Common Pleco, larger carps and minnows, and Pacu fish. Avoid smaller fishes that can fit in the mouth of the shark.
  • Optimal Tank Temperature: 72 to 80 F.
  • Water Ph: 6.2 to 7.5
  • Water Salinity: Freshwater
  • Diet Requirement: Omnivore
  • Temperament: Peaceful
  • Minimum Aquarist Level: Intermediate

Iridescent shark catfish are interesting fishes. They are very big fish species that require quite a huge tank to thrive. That is, you have to provide them with quite a large enough tank and suitable water conditions.

Iridescent sharks are quite hardy species of fish that give an aquarist a bit of flexibility when it comes to maintaining the right water parameters. Even at that, maintaining good tank water conditions is still very important in keeping Iridescent Shark catfishes.

More so, you need to ensure a lot of things are in order and they include the following:

Size of Tank

To keep an adult iridescent shark, you need a tank size of at least 400 gallons to house a single one so it can get enough room to swim around and be comfortable.

Most Aquarists keep the iridescent shark in smaller tanks when they get them initially and then transition them to a bigger tank with time. Though this strategy is nice it is better to make the switch before it becomes paramount. Of course not after, to avoid stressing the fish.

Some owners usually perform the transition after they realized they are getting bigger for the initial tank they were kept in and then start looking for a new tank to move them over. It is bad and may affect the health of your pet fish.

You are always going to need a bigger tank to house this fish so it is advisable to prepare ahead. As such, for greater success, prepare a tank of about 1200 gallons. Your Iridescent Sharks and their tank mates will be happy in this.

Water Temperature:

Maintain a temperature of 72 – 80F to keep the fish happy.

PH Level

It is critical to keep the pH level of the water at 6.2 -7.5 to secure the overall health of the fish as anything below may affect them. The recommended method to test for PH levels is to use a digital PH tester.

Hardness of water

2- 20dGH is the degree of water hardness required. In general, this scale represents somewhere between soft and medium-hard water.

Water Movement/Filteration

Iridescent shark is a migratory species that prefer currents in their water. Therefore, water movement is very essential since they spend hours in front of the outlet of a strong water filter.

As such, get a strong water filter that will maintain water steadiness and also provide adequate oxygen for the iridescent shark.

As an aquarist that cares for his pet fish, always maintain the right water conditions for the fishes and to ensure that, make frequent use of your testing kit.

Aquarium Hardiness: Difficult because of their nervous nature, they tend to get stressed easily.

Level of Aquarist: Aquarist has to be an expert or at the intermediate level because of how big the Iridescent shark gets and the size of the aquarium. Not to mention their neurotic nature.

Tank Region: Iridescent shark, unlike all other catfishes, do not spend most of their time at the bottom of the river, they hang around in the middle and sometimes come to the surface to get petted.

Water Chemistry and Salinity

These fish species are not all too fussy about water salinity as long as the water is clean. However, they do prefer to be kept in soft acid freshwater conditions.

Water Changes

This fish is a bit messy and would leave uneaten foods in the tank. Therefore, Water changes should be done every week. Change at least 25% of water weekly to avoid the water breeding germs that may cause harm to your fish.

Keep a powerful filter in the aquarium of the iridescent shark because these fishes are a bit messy. They leave uneaten foods in the tank. The poops of iridescent fish contaminate the water of the tank and can only be rectified by a good filter.

Nano tank suitability: Not suitable for Nano tanks.

Lighting Need

Iridescent shark requires moderate lighting to Normal tank lighting. We know these shark species can get easily stressed. Even more, at the juvenile, these fish require low lighting until they are well acclimated and comfortable.


Pangasius Catfish are always available at pet stores and online. Their prices are moderate due to their population and availability. And, they are being bred in commercial fish farms. Even while their population is decreasing in the wild, they are still common to the aquarium trade.

Variations: There is an albino iridescent shark

Tank Cleaning Method

Ensure you clean the tank at least twice a month. If iridescent sharks are not kept in a clean environment, they acquire various types of diseases. As a result, get a brush, a cleaning soap, and a cotton cloth to clean the tank thoroughly.

After washing and brushing the dirt, wipe the walls out and the ornaments of the tank with a clean cotton cloth.

Tank Decorations

Iridescent Shark is different compared to all other fish breeds. Thus, it does not require many rocks or plants in its aquarium. Though, you can add some fast-growing plants like Hornwort and Anacharis in the tank.

Provide a soft sandy substrate at the bottom of the tank. If at all you would like to use Rock, use a crushed rock. Ensure you do not place sharp objects in their tank as this may hurt your fish’s delicate body. Pebbles are not necessary for the iridescent shark catfish aquarium.

Iridescent Shark freshwater

Pangasianodon hypophthalmus aka iridescent shark is a freshwater fish usually found in South Asian.

Iridescent Shark Eye problems

An iridescent shark tends to have poor eyesight as they grow older. You cannot totally eliminate it since it is genetic. Nevertheless, be sure you are not the cause of it. Always check water conditions.

Due to their poor eyesight, do no go dipping your fingers into its tank. Of course, it may mistake your fingers to be food and this will lead to biting.

How to Acclimate Iridescent shark catfish

It is no news that if you do not acclimate your fish properly to a new aquarium, it may lead to their death.

As much as many aquarists would like to blame the pet store for selling fish with poor health to them. It is, however, very important that aquarists also ensure they are not the reason why their fish is dying.

Therefore, learning how to properly acclimate your fish cannot be overemphasized. There are two methods for acclimation. We have the float method and the drip method. In this article, we would only be teaching you the float method.

The Float method of Acclimation

  1. Ensure you turn off the aquarium light and dim the light in the room you set up your aquarium. And, this must be done before you remove your fish from the container because your fish may be sensitive to light and can get traumatized by sudden exposure to it.
  2. Float the container your fish came within on the tank water for 15 minutes. Be on the watch out for the container to make sure it does not come undone. By this time, the water in the bag would start to assume the same temperature as the water it is being floated in.
  3. Cut the bag underneath the metal clip keeping the bag closed. If the fish is heavy, you may need to place the bag in a floatable device such as a Tupperware container.
  4. Add water to the container every 4-5 minutes and allow to float for another 4 minutes. Continue until the container gets filled up
  5. Discard half of the water and let the container float again. Once it is full, take it out. Discard the water and put it back in the quarantine tank. Allow the container to start floating again.
  6. Add water from the tank every 4-5 minute, Repeat the process until the container is full.
  7. Let out the fish into the tank. You may need a net at this point. Lower your net into the container and get your fish into it. Gently lift it out and place it into the tank. Be gentle as you do not want your fish to get entangled in the net. Also, be quick when you are transferring your fish into the net. I’m sure you do not want your fish to be out of water for too long!

Iridescent Shark Diseases

Although iridescent sharks are a hardy fish, they are still prone to various diseases. Most Especially, they get stressed easily which may cause their immune system to fail and become vulnerable to infections.

Always make sure you try as much as you can to replicate their natural habitat in your aquarium. Iridescent shark is prone to diseases such as fungal infection and ich. Ich is easily identified by white patches on the body of your fishes that may cause them to rub themselves on any solid substance it can find inside water.

This is usually a result of the fact that your fish does not have a scale. Thus, making it vulnerable to ich and other external injuries. To treat ich, veterinary experts recommend that you use half strength of medication recommended for scale-less fish.

An example is melafix, this comes handy when it comes to treating infections and ich. You can also raise the temperature of the water a little to help ease the itching your sharks may experience. Always ensure your tank is properly cleaned as well.


As you can see in this article, the iridescent shark is beautiful fishes to have. Although, we may not recommend it for the home aquarium. They would still do well should you decide to provide a huge tank for them to swim and be comfortable.

Above all, your decision to keep the Iridescent shark catfish in your home aquarium lies in your disposition to provide it with the required care.

While the Iridescent shark is a great aquarium pet fish, there are other Freshwater Sharks that will make your tank stand out.