Iridescent Shark 101: Size, Tankmates, Care Guide & All | 2023

By: Martin McAdam
Updated: March 20, 2022

Iridescent Shark (Pangasianodon hypophthalmus) is a small shark from the family "Squalidae" or dogfish sharks.

In New Zealand, they are found on the north and west coasts, but the species inhabits all around Australia and southern Japan, China, the Malay Peninsula, and the Indian Ocean.

These sharks are not dangerous for humans because their mouth is located on the underside of their head, and they don't possess a large number of sharp teeth.

Their adult length varies from 1.2 to 2.4 meters (3.9 – 7.9 ft.) and weight from 5 – 55 kgs (11 – 121 lbs.). They have a cylindrical body with two dorsal fins almost equal in size as well as a large, lunate caudal fin.

The skin coloring can be grey, greenish-brown, or dark brown with lighter spots and streaks that give the impression of marbling hence its common name "marbled catshark."

Iridescent sharks are known for producing a weak electric field and sensing any changes in water movement and pressure.

This allows them to either avoid predators or sneak up on prey undetected. They are mostly bottom-dwellers, but they can also be seen in open water near the shoreline.

These sharks are omnivorous and feed mainly on crustaceans, mollusks, worms, and small fishes. Juveniles feed mainly on plankton, while adults consume more benthic organisms.

Iridescent shark is oviparous, meaning that females lay eggs externally. The gestation period lasts for about 10 months, after which 2 – 4 young ones are born, measuring about 20 cm (7.9 in) in length. They are independent of birth and fend for themselves from the moment they enter the water.

Iridescent sharks are not a common sight in the aquarium trade, but they occasionally turn up for sale. They can be kept in an aquarium of at least 200 liters (53 gallons) with a sandy substrate and plenty of hiding places.

They are peaceful fish and will get along well with other species provided there is enough space. Iridescent shark is a beautiful fish that can be a great choice for the intermediate aquarist. The only drawbacks are its rather large size for a relatively small aquarium and continuous difficulty to find in stores.

In my opinion, iridescent sharks deserve the same level of attention as other "sharks," such as leopard sharks or bamboo sharks that can be easily found at your local fish store. So if you're lucky enough to come across one, be sure to snatch it up before someone else does!

To know more about this beautiful creature, let's dig in more.

Facts And Characteristics Of Iridescent Sharks

Given below are a few facts and characteristics Of Iridescent Sharks.

How Do Iridescent Sharks Look Like?

They have a cylindrical body with two dorsal fins almost equal in size and a large, lunate caudal fin. Their fins have a black edge and black tips, except their caudal fin, which is dark grey.

Iridescent Shark

The skin coloring can be grey, greenish-brown, or dark brown with lighter spots and streaks that give the impression of marbling hence its common name "marbled catshark."

As they grow old, their skin will take on a yellowish tinge, developing numerous white patches. When they are young, iridescent sharks are green or grey with dark spots.

These dark spots are more pronounced on the young of the year, while adults have speckled greenish backs and light bellies.

These crystals are made of guanine, and their shape reflects different wavelengths of light. The shark uses this shiny skin to dazzle and confuse prey while hunting in shallow areas where it's often partially exposed.

Their mouths can open very wide, allowing them to swallow large food items. Their teeth are small and needle-like, allowing them to grip slippery prey like eels and other fish.

Adult males tend to be smaller than adult females, but this is only noticeable when comparing large specimens of each sex. Males also develop visible pores on their head and along the sides of their body which are used to release pheromones during courtship.

Their looks can also vary depending on their habitat, like the leopard shark, which gets its spots from where it hangs out and what it eats. Also, the iridescent shark is one of the few sharks that can fluoresce under ultraviolet light, making it glow in the dark!

Average Lifespan And Growth Of Iridescent Sharks

Iridescent sharks can live up to 20 years, and this is largely due to their ability to regenerate damaged tissue. They also heal quickly from injuries and infections, and they don't get cancer!

Lifespan And Growth Of Iridescent Sharks

Their lifespan is the longest among all sharks. Male sharks can live up to 15 years while females live up to 30 years.

Iridescent sharks can grow up to 1.5 meters (4.9 feet) in length and weigh up to 18 kilograms (40 pounds). However, the average size is about 1 meter (3.3 feet) and 8 kilograms (18 pounds).

Usually, female sharks are larger than males. Female sharks can be up to 1.3 meters (4.2 feet) long, while males are up to 1.1 meters (3.6 feet).

When these sharks are born, they weigh around 120 grams (4.2 ounces) and measure about 20 cm (7.9 inches) in length. They are one of the larger "sharks" that you'll find in the fish store, and they require a large aquarium.

Temperament Of Iridescent Sharks

Iridescent sharks are usually docile and inactive, but they can be fierce when feeding. They have very strong swimming ability and can reach speeds of up to 30 kilometers per hour (18 miles per hour).

Temperament Of Iridescent Sharks

When frightened, they will often hide in the bottom of their acrylic fish tank or rocks. They prefer to rest on the bottom of their tank, but they may also swim near the surface if they want to check out what is happening above them.

They like to swim into the currents and will sometimes do so without feeding, which is unusual behavior for sharks.

Their behavior depends on their mood and can vary greatly from one day to the next. One day they can be lazy, and the next, they can be very active.

They are not aggressive to humans unless harassed. Iridescent sharks are considered harmless to swimmers, divers, and snorkelers unless they get extremely close or step on one accidentally, which can cause it to bite out of fear.

When they are frightened, they darken, which makes their skin look almost black. When this happens, you can see the light spots on their skin as if it were a neon sign.

This is caused by involuntary contractions of chromatophores and not for camouflage reasons or to resemble certain patterns of other fish or something like that.

They have photophores on their bellies which are organs that emit light. They are usually used for attracting prey, but the exact purpose of the photophores is unknown yet.

These Sharks are like dogs; they get used to their handlers and recognize them. They can also be trained or at least try to follow moving objects or even people in the tank.

They are very good swimmers, fast and accurate hunters, and can detect dead animals (cut up and left on a hook, for example) from far away.

Habitat Of Iridescent Sharks

Iridescent sharks are native to the rivers of Southeast Asia, where they can be found in the Mekong, Chao Phraya, and Mae Klong Rivers. They are an introduced species in California and have been known to inhabit the Sacramento-San Joaquin River Delta.

Iridescent Shark

Iridescent sharks are found in the Yangtze River and coastal areas of China, where they live in freshwater habitats. They can also be found in brackish water near estuaries and occasionally venture into seawater.

They are not commonly found in the aquarium trade, but they have been exported to Europe, North America, Japan, and other countries.

In the wild, they can be found in depths of up to 2 meters (6.6 feet), but in captivity, they usually stay around the bottom of the tank. Iridescent sharks are tropical species and cannot tolerate cold water.

They require a water temperature of at least 24°C (75°F) in captivity. Iridescent sharks are mainly found on continental shelves and can be observed at depths between 300-900 feet (91 m - 274 m).

They like warm waters that range from 67 to 83°F (19.4 - 28.3°C), and they often stay in the same place, but they don't seem to have a specific territory.

They are usually found in shallow coastal areas. They are most often spotted on the sea bottom or close to it, where they swim slowly with their fins erect.

They are sometimes found near river mouths, but these sharks prefer brackish water to freshwater. Iridescent sharks have been known to enter rivers and estuaries during flood season. These sharks prefer cool, murky waters with plenty of covers from which to ambush their prey.

At this time, there is no conservation status for the iridescent shark. They are categorized as Near Threatened because they are becoming threatened by habitat destruction and pollution of freshwater systems throughout their range.

Although they generally do not enter the same river system twice, hunting them in one river may impact future populations of sharks living in another nearby river.

Breeding Of Iridescent Shark

The mating season for this fish is from March to November. If a female shark cannot find a suitable mate, she may become "virgin pregnant," meaning that she will try to have offspring with other sharks even if it's not the right time for mating.

Iridescent Shark

Sharks can reproduce at any time of the year if they are in captivity. Their gestation period lasts 10 months and can contain up to 4 young ones.

Iridescent sharks reach sexual maturity when they're about 2 years old and 5 feet (1.5 meters) long, but it's better to wait until they are 3 or 4 years old before introducing them in the breeding tank.

They can mate with several partners during the mating season, and the father does not take care of the young.

Iridescent sharks have a polygynandrous mating system in which males mate with multiple females. During courtship, the male shark rubs against the female's body, biting her fins and nipping at her pectoral fins.

They reproduce by laying eggs. After mating, the fertilized eggs are guarded by the male shark until they hatch. The eggs are laid in a sheltered spot on the bottom of the tank and will hatch in about 45 days.

The newly-hatched sharks are independent and can fend for themselves from the moment they're born. There is no relationship between parents and their offspring.

The baby sharks swim away immediately after birth and rarely associate with their mothers or fathers again, even though young iridescent sharks stay in shallow waters for up to 6 months before moving deeper into the water column.

Social Structure

These are schooling fishes. This means that they usually live in groups of up to 12 individuals. Sometimes, larger schools are seen containing up to 200 iridescent sharks.

The school has one male and female leader who mate with each other, but sometimes these roles are shared by different individuals.

When it is time for mating, they form pairs. Sometimes they move around in small groups of 3 - 4 sharks, but they are often found swimming alone or in a pair. They sometimes swim together with other fish species, but they are not known to form alliances with other fishes.

They sometimes act aggressively toward each other when basking in the tank, but this does not mean that they cannot live together with other fish. They are usually the dominant fish in their tank. In a school of iridescent sharks, the largest fish is usually in charge.

They play with other fish and examine them. They become familiar with their owner after time, but they can attack other fish species due to their behavior or differing needs (for example, a school of iridescent sharks could be aggressive toward a betta because that one needs warmer water).

Keeping them together with slow-moving and long-finned fish is not recommended because they can attack them. The iridescent shark will have a hard time swimming with tetras and other fast-moving fish in the tank because their sheer size makes it difficult to maneuver around the smaller fish.

It is not a good idea to keep iridescent sharks in an aquarium with any other sharks due to their uniqueness and the fact that they need different care than other species.

Also, it is not recommended to put them together with any fish larger than them because of their aggressive nature. They mainly feed on fish and crustaceans, so you can try having some in your tank, but there's a chance that the iridescent shark will eat them.

Iridescent Shark Care Guide

The iridescent shark is a beautiful fish that can make a great addition to your tank, but it does require some special care. Make sure you are up for the task before you decide to add one to your tank!

Tank Requirements

Tank size matters because they get big and need lots of swimming room. A 55-gallon tank is a good minimum size for one iridescent shark.

Iridescent Shark

They are not schooling fish, so one is fine, but you will need a much larger tank if you want to keep more than one. When choosing a tank, keep in mind that they can reach 14-16 inches in length and need lots of swimming room.

They need a filter because they produce a lot of waste, and you will also need a clean-up crew to take care of the waste. It is possible to have a tank with just one iridescent shark, but this may require more water changes and maintenance in general.

This fish needs lots of hiding places because their personality can be unpredictable. They are both curious and aggressive, so you need some tall low light plants, rocks, and other decorations to make them feel safe. They like big tanks with lots of open swimming space and hiding places.

They also need an area where they can get out of the water, like a rock that is only partly submerged underwater or some driftwood (you should not use treated wood because it releases poisonous substances into the water).

The tank should be decorated with rocks and driftwood to provide hiding places and make the environment more natural. You should also add plants, but make sure they are sturdy enough to withstand the shark's rasping motions.

If you want to keep more than one iridescent shark in your tank, you should increase the total water volume and capacity of hiding places. You can also add an extra filter to provide even better filtration, as they are sensitive to poor water quality.

The tanks should be placed in a dim area to mimic their natural habitat. You mustn't have bright lights shining on the tank, as it will stress out the shark as it is used to the dark water. A basking light should be set over the tank at one end, with a daylight fluorescent lamp in the opposite corner.

The tank should also have a nightlight so you can easily spot your shark when it's time to feed it. Also, make sure to have a lid on the tank to prevent your shark from jumping out.

Water parameters

Iridescent sharks like water that is slightly alkaline and has a pH of 7.0-7.5. The water hardness should be 10-25 dGH, and the temperature range should be 72-78°F.

Iridescent Shark

The water should be well-oxygenated, and you should change 25% of the water every week. You can use a filter to help with water circulation and add an air pump to increase the oxygen levels.

The right kind of water is important because they are sensitive to poor water quality as well as changes in water parameters. They require stable water conditions to remain healthy.

The water hardness should be 10-25 dGH, which is quite hard. You should use a high alkaline pH buffer to keep the water's pH at 7.0-7.5 and not let it drop below 6.5 or go above 8.0 at any point during the day/night cycle.

Right water conditions are extremely necessary for their health and well-being, and they will not thrive in poor conditions. This shark is only found in Indonesia's very clean, clear waters, and it will be stressed if exposed to dirty water for too long.

Iridescent Sharks Feeding

These sharks are voracious feeders and eager hunters. They mainly eat bony fish, but they will also take crustaceans, cephalopods, or other elasmobranchs.

Iridescent Shark

They hunt in packs to find large prey like sea lions. When it comes to eating, these sharks are very aggressive and excitable. They will often take several bites out of their prey before swallowing it.

They can eat up to 1/3 of their body weight each day in the wild. In captivity, they should be fed 2-4% of their body weight per day.

They eat a lot of different types of food, so they can be a bit picky when it comes to which food you offer them. For the most part, you should feed them a varied diet that includes meaty items such as squid and pieces of fish or shrimp.

If you see there's not much going into your shark's mouth, try offering them a different type of food. In captivity, they should be fed 2-4% of their body weight per day. For the most part, you should feed them a varied diet that includes meaty items such as squid and pieces of fish or shrimp.

Collectively, iridescent sharks are known to prey on bony fish, echinoderms, crustaceans, and mollusks. They will take bites out of virtually any organism that enters their territory.

Individual iridescent sharks have been observed eating strange things too. The most bizarre observation was when an iridescent shark devoured a whole, live rat.

There are a few different foods that you can feed your iridescent shark. It would be best if you gave them a varied diet with live food, pellets, and frozen food.

You need to make sure they regularly eat because when the stomach is empty, it presses up against the spine and causes deformities. One of these deformities is called 'Lumpy Jaw' and can lead to difficulties when eating.

Add in some vitamin supplements to their diet every other day or every third day because they are not getting it on the days that they don't have food.

One of the best things you can feed them is a mixture of dry fish food, boiled peas, carrots, zucchini, and spinach.

Make sure to remove any uneaten food within an hour after feeding because this can cause water quality issues.

Be careful not to overfeed them, as this will also result in poor water quality and can even lead to swim bladder disease if they ingest too much air while eating the excess food.

Adding aquarium salt into their tank is another good way to keep them healthy. It has the same benefits as it does for other saltwater fish, like preventing disease and helping with wounds.

Your iridescent shark will stay healthier if you feed them at least twice a day because their stomach needs time to process food before they ingest too much air. If you only feed them once a day, you are increasing the chances of them getting sick.

Iridescent Sharks can be a great addition to any freshwater tank, but they do require a little extra care. By providing a healthy diet and making sure your tank is in good condition, you can help keep your iridescent shark healthy and happy.

Common Possible Diseases And Their Cure

If the iridescent shark doesn't eat for more than a day, there may be an internal infection or some other medical problem; this is quite serious, and you must see a vet as soon as possible to determine the cause and get treatment.

Iridescent Shark

Some common health problems of iridescent sharks can include:

  • Internal infections
  • Intestinal blockage
  • Flatulence
  • Dropsy (a build-up of fluids in the body)
  • Fin rot (which starts at the tail fins and can result in other fins rotting away too; this is caused by poor water conditions or injury to the fin)
  • Swim bladder disease (caused by lack of vitamin C, which can be due to a poor diet or low water quality)
  • Skin lesions (these can be caused by several things, such as poor water quality, parasites, or bacteria)
  • Parasites (e.g. anchor worms, fish lice, etc.)
  • bacterial and fungal infections

Poor water conditions can cause these diseases. For example, the first three diseases cause problems because of a lack of hygiene and/or low-quality food and water (e.g., a dirty tank with insufficient food vitamins).

The last four usually occur when something is wrong with the water parameters or some other factor that causes stress to the shark.

These diseases are quite serious, so it's important to keep a close eye on their condition when you first get them and make sure your tank is in the best possible condition.

An unhealthy shark could be suffering from any number of problems, so you need to know what the problem is before it can be treated. If not given the right treatment at the right time, it can lead to death.

To keep your iridescent shark healthy, you should include some vitamin supplements in your diet. You will need to give this supplement at least twice a week because they are not getting food containing it on another day or day of the week. Not doing this can result in health issues like fin rot and deformities.

You can either use a liquid vitamin supplement or a tablet supplement. They are both readily available at pet stores. The recommended dosage is 1-2 drops per gallon of water or one tablet per 10 gallons of water.

Other remedies may include Melafix and Pimafix, which are both herbal supplements that reduce the chances of infections and heal wounds. It can be used as a preventative measure to make sure your shark does not get sick.

Also, it is a good idea to add a garlic supplement to their diet as well. Garlic has anti-parasitic and antibacterial properties, and it can help keep your shark healthy.

It's also a good idea to avoid adding in new fish and wait at least six months before bringing new ones into the tank to make sure that your iridescent shark is completely healthy and able to fight off any potential diseases from incoming fish.

Ensure you inspect any new fish's fins for signs of damage or fin rot before you add them to the tank. Your shark will also appreciate some live food, like bloodworms, brine shrimp, and tubifex worms.

Tank Mates Of Iridescent Shark

Keep in mind that iridescent sharks are predatory fish and should not be kept with small fish like guppies. They may also eat other fish that you have in your tank, including invertebrates.

Iridescent Shark

Good tank mates for iridescent sharks include larger fish like cichlids, catfish, and Plecos. You can also add some turtles or other small reptiles to the tank.

Other species that can be tank mates for iridescent sharks include eels, Bala sharks, and pacu. Silver Dollars, Kissing Gourami, Imperial Flower Loach (Leptobotia elongate), etc., are good tank mates for Iridescent Sharks.

To give your shark, good teammates is necessary as they are social fish and need to be around other fish. When selecting tank mates, make sure to get a size range of fish that will make your shark feel comfortable and be big enough not to become prey.

Many owners have a common problem: their iridescent sharks become more aggressive as they grow. You will need to remove your shark and find a new home for it if this happens because once an iridescent shark becomes too large, it can be difficult to handle and keep in a tank.


If you take the necessary steps and care for your iridescent shark properly, you can have a beautiful fish that will bring lots of color to your tank.

Remember, these fish do grow fast, so be prepared to protect them from other fish in tanks as they become too large and cannot be housed with small fish.

Remember to keep the water quality pristine by ensuring you have a good filter. With proper water quality, diet, and tank mates, you will help keep your iridescent shark healthy for many years to come!

This concludes our article on iridescent sharks. We hope you have found it informative. Thanks for reading!

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