The Complete Iridescent Shark Care Guide: Care, Size & Tank Mates

Iridescent sharks (previously Pangasius hypophthalmus, currently Pangasianodon hypophthalmus) are a species of large, freshwater catfish. Which probably seems strange if you only know them as iridescent sharks. In fact, they are also commonly known as Sutchi catfish, Pangasius catfish, and striped catfish.

Iridescent sharks aren’t actually a shark species at all, and they originate from Asia. These fish can grow to be between 3.3 and 4.3 feet in length. They can live for approximately twenty years if given the proper space and a relatively stress-free environment.

Creating such an environment for these fish can be difficult, especially for those new to the hobby of keeping an aquarium. For this reason, they’re not strictly advised for people to keep at home, though an advanced keeper with a large aquarium or outdoor enclosure may be able to successfully keep these fish.

The iridescent shark can be kept relatively happily in a 60-gallon aquarium, but since they prefer to school, you will likely need an aquarium or aquatic space that is at least 40 feet in length, or 300 gallons or more.

Typical Behavior

Iridescent sharks can easily be scared, even as large adults. They’re very skittish and timid, and any movement outside of their environment or space can cause them to make a wild, blind dash to get away from the perceived threat. This can, understandably, be dangerous to them as well as to their tank mates, especially in an aquarium.

This skittishness can cause your iridescent shark to thrash and hit their head or fins on decor in the aquarium or on the glass of the tank itself. It may not be intentionally destructive while trying to escape what it sees as a threat, because these fish have very poor eyesight overall.

If other fish are caught up in the iridescent shark’s attempts to evade danger, they can be hurt as well. It’s important that your iridescent shark feels safe and comfortable at all times as a result.

They like to school as juveniles for safety purposes and may continue to do so as adults, but primarily they should be kept in a school of five or more as juveniles because more aggressive fish may pick on them by biting at their fins.

To alleviate any stress caused by more aggressive species, you should only keep iridescent sharks with large, peaceful fish. There should be a noted emphasis on the fact that these peaceful tank mates need to be large – any fish that the iridescent shark can fit into its mouth as it grows, it will try to consume.

While they are timid and may even play dead if they feel truly threatened, these are very active fish. In their natural habitat, they live in large rivers that have sandy or rocky beds. In these rivers, the iridescent shark tends to stay in the mid-range water layers.

To satiate their need for space and activity, you will want a tank or enclosure that’s on the larger end of the spectrum. If you have difficulty making a large space feel secure for these fish, adding a variety of plants can help.

Also keep in mind that these fish are known jumpers, so it will be necessary to use a tight-fitting panel lid or hood to keep them safe and in the water.

They tend to be more active during the day than other catfish.

Iridescent sharks Appearance

It may be clear by the name, but the iridescent shark is, in fact, iridescent. What this means is that when it moves, the scales can sometimes reflect light in different colors or may simply appear particularly shiny.

This shiny appearance usually fades with age, as do the black strips on and below their lateral lines. The lateral line should be pointed out because it is actually a sensory organ. It’s full of nervous tissue that is used to help the fish detect changes in the water, and may help them identify potential threats.

By the time they are adults, iridescent sharks are actually a fairly uniform gray color. They’re sold as juveniles in part to their more attractive appearance and partially because they become such large fish as adults.

They range from 3.3 to 4.3 feet in length as adults, with the females typically being plumper and larger than the males.

A unique quality of these sharks when compared to other catfish species is that they don’t have the bonier body armor of some other species. These bony plates usually help catfish to protect themselves while still allowing for a relatively free range of motion, but they’re absent in the iridescent shark.

The iridescent shark does have long, whisker-like barbels. The barbels help them to feel out their environment and search for food. This is useful because sometimes these fish are located in low-visibility, low-light, and high-sediment areas, on top of them already not having the best eyesight.

Food and Feeding

Iridescent sharks are omnivorous. This means, in the simplest of terms, that they thrive on a diet of both animal- and plant-based food items. They will take any offered food item under the most favorable circumstances. These fish will feed on everything from algae to other, smaller fish.

As juveniles, you can supplement the diet of the iridescent shark in several ways with a varied diet. With naturally-blooming algae or algae wafers, seed plants, zooplankton, small insects, and tropical flake or pellet foods your juvenile iridescent shark should be healthy and have a well-rounded diet. As they age and become adults, they will also accept small fish, certain fruits, and crustaceans as well.

Additionally, they will also take frozen food items such as bloodworms and brine shrimp. Feed these items every two or three days to keep your fish interested in different foods, as it will keep them healthy and active.

Many keepers will feed these fish a higher-protein diet as juveniles and move on to a more plant-based diet for the adults, as the iridescent shark may begin to lose their teeth the older they get. Be sure to keep this in mind and feed appropriately.

If you choose to offer your iridescent sharks live feeders, such as comet goldfish, minnows, or guppies, be sure that you buy them from a local pet store and quarantine them in a separate tank for three to five days. This will ensure that they are healthy and won’t pass on any illnesses, parasites, or other ailments to your sharks.

Tank Setup

When you choose to get an iridescent shark, or more appropriately a school of them, you need to know first that you have the appropriate set-up for them.

Tank Size

A singular iridescent shark can live comfortably with tankmates in an aquarium that is at least 40 gallons. However, it’s advised to give these fish much more space to roam and be active. This is especially true if you have a school of four to five iridescent sharks, which will need an aquarium of at least 100 gallons as juveniles and at least a tank size of 300 gallons as adults. Add approximately 150 gallons worth of space for each additional iridescent shark.

Since they come from wide, large rivers in the wild, you want to simulate that environment’s space to the best of your ability. Provide an open swimming space, especially along the middle layers of the space, and add driftwood and rocks to the bottom of your tank where the substrate is.

Additionally, since they are skittish particularly as juveniles, you may want to add some plants. Specifically, floating plants are a great option for reducing stress in these fish and gives them a sense of safety. They also prefer softer substrates, such as mud or sand.

Water Parameters

As is the case with most fish, iridescent sharks do not tend to respond well to frequent changes in their water quality or the parameters of their tank. While they are hardy, they are not invincible and are very vulnerable to high levels of stress. So to ensure a high quality of life for your fish, you need to make sure that you can maintain the correct parameters for their needs.

The pH should be between 6.5 and 7.5 in the aquarium. Anything in that range is safe, but once your fish have become accustomed to a particular pH balance, try not to let it fluctuate too much.

You should keep the temperature of the water somewhere between 72 and 79 degrees Fahrenheit. If possible, you can gradually adjust the temperature of the water to mimic seasonal changes, but don’t venture beyond these parameters as it will upset your fish. Put the heaters in places where the fish cannot accidentally break them if they get scared or skittish – undergravel heaters or external in-line heaters work well.

The water hardness may be something that you do not typically think of as a factor for your fish unless you keep particularly sensitive species, but the iridescent shark does have a preference. They prefer water within the range of 2 to 20 dGH. The GH is the measurement of the level of magnesium and calcium that is dissolved in the water.  

Lighting

Iridescent sharks prefer a moderate amount of light. This is usually fine for some fast-growing plants that may give the sharks an additional sense of security, such as hornwort or anacharis. These plants should grow fast enough that even if your fish are nibbling on them, it shouldn’t be noticeable.

Water Flow and Filtration

You will need a powerful filtration system in place while keeping this kind of fish, as they produce a significant amount of organic waste. External filters are preferred for these fish and their tank mates because they typically also provide the level of water flow that the iridescent shark prefers.

If your external water filter is not creating a moderate level of water movement or flow, you may need to add an additional air pump to generate the appropriate amount of circulation that your fish need and enjoy.  

As previously mentioned, iridescent sharks are particularly messy by nature. But to keep them both happy and healthy, their water needs to be clean and manageable. This can be difficult, so you’ll want a powerful external filtration system to handle most of the work for you.

You also want to make sure that you do weekly water changes.

About 25 to 30 percent of the aquarium water will need to be changed each week, and since iridescent sharks require a large tank to thrive in, this can be a time-consuming activity. This is especially true since you want to change the water slowly to avoid scaring your fish unnecessarily.

Iridescent Sharks Tank Mates

As previously stated, aggressive tank mates should be avoided particularly while your iridescent sharks are in their juvenile and adolescent stages. The tank mates of your iridescent sharks should be large, peaceful fish that can also be schooling fish if you’d like. You want to look for species of fish that are large enough or will be large enough that they won’t be eaten by your iridescent sharks.

There are many large peaceful or semi-aggressive, but not overtly so, fish that will make good companions and tank mates for your iridescent sharks. These include:

• Kissing gourami
• Silver dollars
• Plecostomus
• Salvin’s cichlids
• Some other large catfish species
• Fire eels
• Bichir
• Texas cichlids

The iridescent shark can live with any non-aggressive or semi-aggressive fish of a similar size and which will not harass the shark itself. It should not be housed with fish with a low activity level, as it may agitate those fish.

Iridescent sharks should also not be housed with crabs, shrimps, or snails. As soon as they can, they will begin to eat these tank inhabitants, so unless you’re maintaining a population in a separate tank and feeding off the excess crustaceans to your iridescent sharks, it’s not advised to keep them with these fish.

Breeding

To date, there have been no successful breedings of iridescent sharks in captive aquarium environments. This is because of the spawning habits of the fish and the sheer size of the adults. This fish is migratory and will travel upstream from its normal habitat to spawn in the late spring and summer months.

This behavior coupled with the size of the fish makes it nearly impossible to duplicate amicable breeding conditions in captivity. It should also be noted that, while there is sexual dimorphism in the adults of this species, it’s much more difficult to distinguish the differences at a juvenile age. Since this is the age most pet stores will sell these fish at, you’re not guaranteed the sex of the fish you will receive.

Iridescent sharks are bred and produced in huge ponds in Southeast Asia, in places like Singapore and Thailand. They may also be harvested from wild populations and then raised in large, floating containers.

Diseases

Iridescent sharks, like most fish, are susceptible to several common diseases, including fungal diseases. As a scaleless catfish, if they happen to contract ich, they can be difficult to treat without prior experience. Most ich cures will advise you to use a half-strength dose to treat your catfish, which may prolong exposure and infection risk to other fish in the tank.

An easier solution is to use treatments such as Pimafix or Melafix to treat your infected tank, depending on appropriateness, if iridescent sharks are in the tank. Use these medications as directed, and if you are uncertain, do not hesitate to contact the manufacturer or company behind the medicine to ask them any questions or concerns that you may have.

Since iridescent sharks are easily frightened, they’re liable to scratch themselves trying to escape things that they believe to be threats. And since they’re a scaleless species, it’s important to be ready to treat them for any injuries they cause to themselves. For this, you’ll want to use some slime coat replacement such as Stress Coat or NovAqua.

Be sure that you avoid using medications for these fish that are based on copper or potassium permanganate. These chemicals can be dangerous for your iridescent shark. You can, however, use malachite green or formalin, just make sure you use either a quarter or a half of the recommended dosage.

Remember that all medications for your fish should be used with caution. Double-check with a veterinarian familiar with aquatic animals or with the manufacturer of the medication for any safety questions or concerns.

Are Iridescent Sharks Suitable For Your Aquarium? (Summary)

In conclusion, iridescent sharks can be a rewarding species to keep so long as you keep them happy, healthy, and stress-free. But, they are also difficult to keep, and the space they require alone for long-term keeping rules them out as good fish for most hobbyists. Additionally, even when you can afford the space and maintenance that they require, they have a lifespan of twenty years, so you have to plan for long-term care of these large fish.