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Iridescent shark
Iridescent shark
Iridescent shark
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Iridescent shark
CITES Appendix I [2]
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Siluriformes
Family: Pangasiidae
Genus: Pangasianodon
Species:
P. hypophthalmus
Binomial name
Pangasianodon hypophthalmus
(Sauvage, 1878)
Synonyms

Helicophagus hypophthalmus Sauvage, 1878
Pangasius sutchi Fowler, 1937[3]
Pangasius hypophthalmus (Sauvage, 1878)

Global aquaculture production of Pangasianodon hypophthalmus in million tonnes from 1950 to 2022, as reported by the FAO[4]

The iridescent shark or iridescent shark catfish[5] (Pangasianodon hypophthalmus) is a species of shark catfish (family Pangasiidae) native to the rivers of Southeast Asia. Despite its name, it is not a shark. It is found in the Mekong basin as well as the Chao Phraya River, and is heavily cultivated for food there.

The meat is often marketed under the common name swai (from Thai สวาย). It has also been introduced into other river basins as a food source, and its striking appearance and iridescence have made it popular with fishkeeping hobbyists, among whom it is also known as the Siamese shark catfish or sutchi catfish.[6] The swai's omnivorous diet consists of crustaceans, other fish, and plant matter.[7]

Names

[edit]

The fish is named for the glow or iridescence exhibited in juveniles, as well as the shark-like appearance of this and other shark catfish.

Description

[edit]

Adults reach up to 130 cm (4.3 ft) in length and can weigh up to a maximum of 44 kg (97 lb). They have a shiny, iridescent color that gives these fish their name. However, large adults are uniformly grey. The fins are dark grey or black. Juveniles have a black stripe along the lateral line and a second black stripe below the lateral line.[7]

Distribution and habitat

[edit]
P. hypophthalmus migrations in the Mekong River Orange: March to May
Dark green: May to September
Red: October to February
Shaded region: spawning region of the southern Mekong population between Khone Falls and Kratie

Iridescent sharks originate in the large rivers Chao Phraya and Mekong in Asia, though they have been introduced into other rivers for aquaculture. They are a freshwater fish that natively live in a tropical climate and prefer water with a 6.5–7.5 pH, a water hardness of 2.0–29 dGH, and a temperature range of 22–26 °C (72–79 °F).[7] They can tolerate hypoxic conditions thanks to their swim bladder which can be used as an air-breathing organ.[8] They prefer large bodies of water similar to the deep waters of their native Mekong river basin.

The iridescent shark is a migratory fish that in most regions moves upstream to spawn during the flood season while the waters are high and returns downstream to seek rearing habitats when the river water levels recede. The dates of the migrations vary depending on the river system. In the Mekong river basin, they migrate upstream in May to July and return downstream during September through December. South of the Khone Falls, upstream migration occurs in October to February, with its peak in November to December; here, it appears to be triggered by receding waters at the end of the flood season.[7]

In August 2015, an environmental group in Santander, Colombia, confirmed that iridescent sharks had been found in one of the tributaries that feed into the Magdalena River, having been accidentally introduced from illegal farm fisheries in the area. The find has caused alarm amongst the scientific community and government officials, as the Magdalena river is home to over 200 native fish species, 35 of which are endangered.[9]

Disruption to these sharks can come from many physical stressors, including but not limited to shear forces, rapid decompression, blade strike and turbulence. These can lead to and have led to an increase in the Injury and mortality rate of these sharks. This is a sad reality[citation needed] since these injured can be caused by hydropower developments which are being put into place to combat the global climate crisis that is being faced.[10] Iridescent sharks are also introduced to other Southeast Asia countries for food, especially Peninsular Malaysia, Singapore, Indonesia and Myanmar. In Malaysia, Singapore and Indonesia they are called ikan patin (which 'ikan' means fish in Malay and Indonesian), Malaysian Chinese prefer them steamed or cooked in whole, while Malay prefer cooking these fishes with Tempoyak and curry.[11]

In Thailand, swai fish are commonly found in rivers and canals that run past important Buddhist temples or waterside places. Swai live in large schools, sometimes with other fish such as spot pangasius and red-tailed tinfoil with tinfoil barb. Fish that live in that area, people won't catch them, and often feed them (usually bread), which is considered a merit-making and fun activity.[12]

Culinary profile

[edit]
Swai fillet as sold in the United States

Pangasius does not have a gourmet reputation and is sold cheaply as swai (/swaɪ/, from Thai สวาย s̄wāy)[13][14] in the United States, panga (or pangas) in Europe and cream dory and basa in several Asian countries and in Australia and the UK.

Despite its lowly reputation, the total export of pangasius from Vietnam reached US$1.8 billion in 2014.[15]

Pangasius fillets are an increasingly popular product because of their low cost, mild taste and firm texture. Recipes for other whitefish such as sole or halibut can be adapted to pangasius.[16]

Pangasius is an omnivorous fish, and thus does not require a high level of animal protein in its diet. Typical grading sizes are 3–5 oz (85–140 g), 5–7 oz (140–200 g), and 7–9 oz (200–260 g).[17]

In the aquarium

[edit]
A juvenile Pangasianodon hypophthalmus

While juvenile iridescent sharks are sold as pets for home aquariums, they are not easy fish to keep. Iridescent sharks are schooling fish that prefer groups,[7] are accustomed to living in rivers, and are active fish that require space. They have very poor eyesight, so detected movement from outside of their habitat can be seen as a threat. If stressed, their first instinct is to flee; a blind dash can cause injury in an aquarium environment. These injuries may result in the fish sinking to the bottom, where it may lie on its side or back until it recovers.[18]

Iridescent sharks require a minimum tank size of 12 m (39 ft) to develop naturally. Schools require even larger tanks. If given enough room and fed adequately, they can reach 1 m (3.3 ft) in length. In most home aquaria, the lack of space stunts their growth. For this reason, most iridescent sharks kept in home aquaria grow to 15 to 30 cm (6 to 12 in) in length only and may die prematurely. When provided adequately sized aquaria and proper husbandry, iridescent sharks may live into their teens and grow to full size.[19]

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Iridescent shark

View on Grokipedia
from Grokipedia
The iridescent shark (Pangasianodon hypophthalmus), commonly known as the striped or sutchi , is a large freshwater belonging to the Pangasiidae, native to the river basins of . Despite its shark-like appearance and name, it is a true with an elongated, streamlined body, dark grey or black fins, and six branched dorsal-fin rays; juveniles exhibit distinctive black lateral stripes that fade to a uniform grey in adults. This facultative air-breathing can attain a maximum standard length of 130 cm and weight of 44 kg, inhabiting benthopelagic zones in tropical freshwater environments with temperatures of 22–26 °C, pH 6.5–7.5, and hardness 2–29 dH. The species is primarily distributed in the River basin across , , , and , as well as the Chao Phraya and basins in , where it undertakes seasonal migrations—upstream from May to for spawning and downstream from to December. It thrives in main channels of large rivers, shifting to floodplains and marshy areas during the rainy season floods, and has been introduced to other regions for purposes. Ecologically, P. hypophthalmus is omnivorous, feeding on , crustaceans, , and debris, and it plays a key role in the Mekong's as one of the basin's most abundant migratory species. Economically, the iridescent shark is a cornerstone of in the , particularly in , where it is intensively farmed in ponds, cages, and rice fields, contributing to global production exceeding 2.9 million tonnes annually as of 2023 and supporting major exports under names like swai or basa. It is also popular in the ornamental for its iridescent juvenile coloration and active schooling , though its rapid growth to over 1 meter makes it unsuitable for most home aquariums, often leading to challenges in . Conservation-wise, wild populations of P. hypophthalmus are classified as Endangered by the IUCN due to a significant decline in abundance and range contraction, with catches in the Cambodian dropping from 237 metric tonnes in 2000–2001 to just 4.7 metric tonnes in 2017–2018, alongside reductions in mean length and larval/juvenile densities. Primary threats include , from hydropower dams, degradation, and altered flood regimes, though has alleviated pressure on wild stocks while raising concerns about escapes and genetic impacts. Efforts focus on protecting migratory routes, enforcing regulations, and maintaining seasonal flows to support recovery.

Taxonomy and names

Taxonomy

The iridescent shark, scientifically known as Pangasianodon hypophthalmus (Sauvage, 1878), is a species within the family Pangasiidae. Its reflects its original description by French ichthyologist Henri Émile Sauvage in 1878, based on specimens from Southeast Asian rivers. The taxonomic classification of P. hypophthalmus is as follows: Kingdom Animalia; Phylum Chordata; Class ; Order Siluriformes; Family Pangasiidae; Genus Pangasianodon; Species P. hypophthalmus. This places it among the ray-finned fishes, specifically within the diverse order of catfishes (Siluriformes), where the Pangasiidae family is noted for its shark-like catfishes. Accepted synonyms include Helicophagus hypophthalmus Sauvage, 1878 (the original combination), Pangasius hypophthalmus (Sauvage, 1878), and Pangasius sutchi Fowler, 1937, reflecting historical reclassifications as understanding of the genus evolved. The genus name Pangasianodon derives from Pangasius (a related catfish genus) combined with the Greek privative prefix an- (without) and odon (tooth), alluding to the toothless state of adults in this group. The specific epithet hypophthalmus comes from the Greek hypo- (under) and ophthalmos (eye), referring to the ventral position of the eyes on the head. Despite its common name, P. hypophthalmus is not a true but a , with the "shark" moniker arising from the family's Pangasiidae designation as shark catfishes due to superficial resemblances in body form and dentition to elasmobranchs.

Common names

The iridescent shark is referred to by several English s, including iridescent shark, iridescent shark catfish, and striped catfish. Regionally, it is known as sutchi catfish in , where the local name is pla sawai. In , particularly in countries such as , the , and , the species is commonly called . In the United States, it is marketed as swai, though frequent confusion with the related species Pangasius bocourti leads to mislabeling as basa. In aquaculture and international trade, fillets of this species are often sold under the trade names swai or basa, contributing to widespread misidentification between Pangasianodon hypophthalmus and similar pangasiid catfishes. The term "iridescent" originates from the shimmering, rainbow-like sheen on the scales of juvenile specimens, while "shark" reflects the species' elongated, streamlined body shape that mimics true sharks, even though it belongs to the catfish genus Pangasianodon.

Description and biology

Physical description

The iridescent shark (Pangasianodon hypophthalmus) has a streamlined, shark-like body that is elongated and strongly laterally compressed, with a depressed head, rounded , and a long caudal peduncle; it lacks an adipose fin and possesses smooth, scaleless skin covering the body. The mouth is broad and terminal, equipped with small sharp teeth on the jaws, vomerine, and palatal bones, along with two pairs of barbels—the maxillary pair longer than the mandibular pair, extending beyond the opercle but not reaching the pelvic base. The is single and positioned near the head with 6 branched rays, while the anal fin has a long base with around 34 rays, and the caudal fin is forked; pectoral and pelvic fins are present but unremarkable. This species attains a maximum standard length of 130 cm (approximately 4.3 ft SL) and a weight of up to 44 kg in the wild and settings. In home aquariums, individuals typically reach 60-100 cm if provided with sufficient space, though growth can be stunted in undersized tanks, leading to smaller adult sizes and potential health issues. Juveniles display striking iridescent blue-green coloration on the sides, accented by two prominent black stripes—one along the and a second parallel below it—along with dark grey or black fins. As adults mature, the iridescence and stripes fade, resulting in a uniform grey body (sometimes with a greenish tint) and silvery sides, while the fins remain dark; the oval eyes are relatively large but positioned ventrally, slightly below the body's horizontal axis. Owing to the ventral eye placement, P. hypophthalmus has limited and relies heavily on its sensitive barbels and system for detecting prey, obstacles, and environmental cues in turbid waters. The also features a highly vascularized adapted for air-breathing, which enhances its tolerance to low-oxygen conditions by allowing supplemental atmospheric respiration. Sexual dimorphism is minimal outside of the breeding season, but ripe females become noticeably larger overall and develop a rounder abdominal profile compared to males.

Behavior and diet

The iridescent shark, Pangasianodon hypophthalmus, exhibits schooling behavior, forming large groups especially during juvenile stages and maintaining this into adulthood to enhance predator avoidance and efficiency in riverine environments. As active swimmers, individuals constantly patrol main channels and plains, contributing to their migratory lifestyle during seasons. When stressed, such as by environmental disturbances or threats, they display erratic fleeing responses, including sudden dashes and jumps, which can result in injuries from collisions with obstacles or conspecifics. Although primarily diurnal in activity, iridescent sharks prefer low-light conditions, aligning with their native turbid river habitats where visibility is limited; this preference is evident from higher feeding success in dim or dark settings, reducing predation risk while allowing chemosensory foraging. Seasonal migrations occur in response to water level changes, with upstream movements during rising floods and downstream dispersal as waters recede, facilitating access to feeding and spawning grounds during seasonal flood cycles. This species is omnivorous, with wild diets comprising , , crustaceans, small , and vegetable debris, showing ontogenetic shifts where juveniles exploit in hypoxic profundal zones and adults target mid-water planktonic sources via photosynthetic food chains. As bottom- and mid-water feeders, they rely on two pairs of barbels equipped with for chemosensory detection of prey in murky waters, compensating for their relatively poor eyesight and enabling opportunistic ingestion even in low-visibility conditions. In captivity, such as settings, they thrive on formulated diets including commercial flakes, sinking pellets, frozen or bloodworms, and algae-based wafers to mimic natural omnivory and support growth.

Reproduction

The iridescent shark (Pangasianodon hypophthalmus) exhibits potamodromous migration for reproduction, undertaking large-scale upstream movements in the River basin during the season from May to August, with peak spawning in late June and early July. This migration aligns with rising water levels, enabling access to shallow, vegetated spawning grounds in the upper Cambodian between the Khone Falls and Kratie. Spawning involves the broadcast of , demersal eggs over aquatic vegetation and roots, where they attach and develop. Sexual maturity is reached at 2–3 years of age, with males maturing earlier (around 2 years) and females later (3 years); individuals typically attain lengths of 40–50 cm at this stage. The species is highly fecund, with a mature female weighing 10 kg capable of producing over 1 million eggs per spawn, though exact counts vary by body size and condition. Eggs are spherical, greenish-brown, and measure 1.00–1.70 mm in , featuring a prominent . Following fertilization, eggs hatch in 18–24 hours at temperatures of 26–30°C, yielding pro-larvae approximately 3 mm long that initially rely on reserves. Larvae remain pelagic for the first few days, actively swimming in the before the is absorbed (within 24–48 hours) and they transition to exogenous feeding on . By 72 hours post-hatch, larvae develop into fry (about 7 mm long), schooling in shallow, protected nursery areas such as shallows. Post-spawning, adults migrate downstream to feeding grounds in the , completing the reproductive cycle. Captive breeding is rare in aquariums due to the species' large adult size (up to 1.3 m), but it is routinely induced on farms using hormonal treatments such as extract (2–10 mg/kg body weight) or LHRH analogs (0.15–0.60 ml/kg), achieving fertilization rates of 88–90% and hatching rates of 72–78%. These methods simulate natural spawning cues, with occurring 8–15 hours after injection, and are essential for seed production in regions like .

Distribution and habitat

Native distribution

The iridescent shark (Pangasianodon hypophthalmus) is native to the River basin, spanning , , , and , as well as the Chao Phraya and Maeklong River basins in . This distribution reflects its historical presence in interconnected large-river systems of , where the species undertook extensive migrations for spawning and feeding before the construction of dams altered river connectivity. Prior to widespread damming in the mid-20th century, the iridescent shark was distributed across vast stretches of these river basins, with populations migrating upstream to spawn in and downstream to floodplains for growth. from developments, such as those on the mainstream, has since restricted movements and contributed to a sharp decline in wild populations, with catch rates dropping significantly over recent decades. Today, while wild stocks persist at low levels in remnant river segments, the species' abundance is overshadowed by intensive production, which supplies the majority of global stocks. Genetic studies reveal distinct subpopulations adapted to specific river stretches within the native range, such as spawning aggregations in the upper and growth areas in the delta, highlighting the ' evolutionary specialization to varied basin conditions. These adaptations underscore the vulnerability of wild to ongoing fragmentation and hybridization with farmed strains.

Habitat preferences

The iridescent shark (Pangasianodon hypophthalmus) is a tropical freshwater species that thrives in environments with temperatures ranging from 22 to 26 °C, levels of 6.5 to 7.5, and water between 2 and 29 . These parameters reflect its adaptation to the dynamic conditions of large river systems, where it functions as a benthopelagic , occupying both bottom and mid-water zones. In its preferred habitats, the species favors deep river channels and expansive floodplains that become accessible during seasonal flooding, allowing movement for feeding and dispersal. Juveniles, post-spawning, drift downstream and utilize shallow, vegetated margins of these flooded areas as nursery grounds, providing cover and abundant food resources. In contrast, adults predominate in the deeper, swifter currents of main river channels, where they exhibit migratory behavior to exploit varying ecological niches. Key adaptations enable the iridescent shark to endure the variable conditions of its habitats, including facultative air-breathing via a highly vascularized that supplements respiration in low-oxygen waters. This physiological trait supports tolerance to dissolved oxygen levels as low as 0.05–0.10 mg/L, common in , hypoxic river segments during dry periods or high flows. Additionally, the species shows resilience to elevated and fluctuating , characteristics of silt-laden tropical rivers.

Conservation

Status and threats

The iridescent shark (Pangasianodon hypophthalmus) is classified as Endangered (EN) on the of Threatened Species, based on a 2011 assessment under criteria A2bd+4bcd, which reflect an observed, estimated, inferred, or suspected population reduction of at least 50% over the past three generations due to declines in habitat quality and levels of exploitation. This classification remains current as of the 2025 IUCN Red List update, with no major reassessment indicating a change in status. Major threats to wild populations stem from anthropogenic activities in the and Chao Phraya basins. dam construction, such as the Xayaburi and Lower Sesan 2 dams, fragments habitats and obstructs migratory pathways critical for spawning and nursery access, leading to reduced . , including targeted commercial harvests and intensive collection of juveniles for seed, has intensified pressure on stocks, while habitat loss from and associated degrades and floodplains essential for reproduction. in other riverine fisheries further exacerbates mortality rates among vulnerable life stages. Wild population estimates are limited and vary by region, but overall numbers are declining due to these cumulative pressures. In the Basin, commercial catches of adults have plummeted, with Cambodian landings dropping from 237 metric tons in 2000–2001 to 4.7 metric tons in 2017–2018—a reduction exceeding 98%—reflecting broader stock depletions. Larval and juvenile abundance has also shown a marginal but significant downward trend from 2004 to 2018, supporting inferences of basin-wide reductions in exploitable stocks since the 1990s.

Conservation efforts

In Vietnam, regulations prohibit the capture of wild juveniles of the iridescent shark (Pangasianodon hypophthalmus) for stocking, with Vietnam fully transitioning to hatchery-produced seed to protect declining wild populations. These measures aim to reduce , as wild stocks have been severely depleted, and support sustainable management. The River Commission () has implemented initiatives to facilitate , including the development of fish passage structures at dams, such as guidelines for designing effective fishways tailored to migratory species like the iridescent shark. These efforts address barriers posed by infrastructure, promoting connectivity between spawning grounds and feeding areas in the Basin. While specific restocking programs for wild populations remain limited, hatchery enhancements indirectly aid conservation by alleviating pressure on natural stocks through increased production. Research on has informed stock management, with studies revealing high variability in wild and domesticated populations to guide selection and prevent in hatcheries. genomic analyses of samples from major farming countries highlight differences between wild and farmed stocks, supporting strategies for maintaining genetic health. Ongoing monitoring employs acoustic to track adult movements in the River, providing data on migration patterns as of recent assessments. Electrification methods, such as , are used in basin-wide surveys to assess abundance and habitat use. International cooperation through the , involving , , , and , coordinates under the 1995 Mekong Agreement, emphasizing sustainable practices to protect shared migratory species like the iridescent shark. The IUCN's endangered listing underscores the need for regional action plans that promote sustainable to further reduce wild harvest pressures.

Uses

In aquaculture and fisheries

The iridescent shark, scientifically known as Pangasianodon hypophthalmus, is predominantly farmed through intensive pond aquaculture in Vietnam, which has emerged as the global leader in its production. Vietnam's Mekong Delta region hosts extensive pond systems where fingerlings are stocked at high densities, typically 60-80 fish per square meter, and grown to market size of 1-1.5 kg in 6-8 months using formulated feeds and controlled water management. Induced spawning with hormones, such as human chorionic gonadotropin (hCG) or synthetic analogs, is routinely employed in hatcheries to synchronize breeding and produce larvae that hatch within 22-24 hours, enabling year-round farming cycles. Vietnam produced 1.6 million tonnes in 2023 and an estimated 1.75 million tonnes in 2024, accounting for about 50% of global production of 3.4 million tonnes in 2023; as of 2025, Vietnam's production is projected to reach 1.65 million tonnes, with global output expected to grow by 7%. In contrast, wild capture fisheries for P. hypophthalmus have significantly declined since the due to and habitat alterations in the River basin, with commercial catches dropping from hundreds of metric tons per season in the early to 4.7 metric tonnes in 2017–2018, with ongoing declines reported. To mitigate this, supplementary stocking programs release hatchery-reared juveniles into rivers, though their impact on wild populations remains limited amid ongoing threats. Aquaculture now vastly outpaces wild harvests, reducing fishing pressure on natural stocks. Economically, P. hypophthalmus farming drives substantial revenue for , with exports reaching USD 2 billion in 2024, supporting over 1 million jobs in the sector and positioning the country as a key supplier to markets in the United States, , and . Global production contributes to by providing an affordable protein source, though price volatility and trade barriers occasionally affect profitability. The shift toward has enhanced by alleviating dependence on wild captures, yet it introduces challenges such as escaped farmed interbreeding with wild populations and the spread of diseases like bacterial septicemia in intensive systems. Efforts to address these include improved and for disease-resistant strains, promoting long-term viability.

Culinary uses

The iridescent shark, known commercially as basa, swai, or , is primarily marketed in fillet form, with portions typically graded between 85 and 260 grams to suit various culinary applications such as individual servings or family meals. These skinless, boneless fillets are often frozen for export, providing a convenient, ready-to-cook option that maintains freshness during global shipping. The flesh of the iridescent shark is prized for its mild flavor and white appearance, offering a subtle, slightly sweet taste that pairs well with bold seasonings without overpowering them. Its texture is firm yet flaky when cooked, contributing to a tender , while the low fat content—approximately 2-3%—results in a lean profile that avoids greasiness. Preparation methods for iridescent shark fillets are versatile, including with for a charred exterior, pan-frying to achieve crispiness, or for a healthier option that highlights its natural delicacy. In , it features prominently in light, aromatic soups such as Vietnamese or Indonesian , where the fish absorbs tangy and lemongrass flavors. In Western markets, it is commonly processed into fish sticks or fingers, breaded and fried for convenient, kid-friendly meals. Nutritionally, iridescent shark provides high-quality protein at 16-19 grams per 100-gram serving, supporting muscle maintenance and overall health. It is a low-mercury , with levels well below thresholds set by regulatory bodies, making it suitable for regular consumption including by pregnant women and children. Additionally, it serves as a source of omega-3 fatty acids like DHA and EPA, which contribute to cardiovascular benefits despite lower concentrations compared to like . On the global front, iridescent shark fillets position as an affordable alternative to pricier whitefish like or , thanks to efficient farming and processing in . The imported approximately 91,500 metric tonnes in 2023 and over 100,000 metric tonnes in 2024, reflecting strong demand for its economical, versatile protein in retail and foodservice sectors.

In aquariums

The iridescent shark (Pangasianodon hypophthalmus) is a popular but demanding for experienced aquarists due to its rapid growth and need for spacious conditions. While juveniles are often sold in the aquarium trade for their striking appearance, adults require substantial tanks to thrive, as they can reach lengths of up to 90 cm in captivity. them in undersized aquariums can lead to , where they may only reach 15–30 cm, increased aggression, or stress-related health issues. For proper care, a minimum size of 1,135 liters (300 gallons) is recommended for a small group of adults, though larger volumes exceeding 4,500 liters are ideal for a single mature specimen to allow for natural swimming behaviors. The setup should include a soft substrate, scattered rocks or for hiding spots to minimize stress from their skittish nature, and strong water movement provided by a powerful system, such as a sump filter, given their messy eating habits. Moderate lighting is preferable to reduce jumpiness, and the aquarium should feature an open swimming area in the middle water column. Water parameters must mimic their Southeast Asian river origins, with a pH range of 6.5–7.5, temperature of 22–26°C (72–79°F), and water hardness of 2–20 (soft to medium). These conditions support their scaleless skin, which makes them sensitive to poor , necessitating frequent partial water changes and high oxygenation. As omnivores, iridescent sharks should be fed a varied diet including high-quality sinking pellets, blanched like or peas, and occasional live or frozen foods such as bloodworms or to promote health and coloration. Juveniles require more protein-rich foods, while adults benefit from increased vegetable matter; feed 2–3 times daily in small portions to avoid overfeeding and maintain . These fish are shoaling by nature and should be kept in groups of at least 4–5 individuals to reduce stress and prevent individuals from becoming overly timid or aggressive toward tankmates. They are generally peaceful but active swimmers, compatible with other large, non-aggressive like silver dollars or ; however, they may prey on smaller or , so avoid housing with tetras, , or fin-nippers. In captivity, iridescent sharks can live 15–20 years with optimal care, though lifespans are often shorter due to inadequate housing. Common health issues include ich ( ) and , exacerbated by stress from cramped conditions or abrupt parameter changes, which can also lead to self-inflicted injuries from panicked dashing into tank walls. Preventive measures include quarantining new fish and using half-strength medications for treatments, as their sensitive skin tolerates standard doses poorly; juveniles are preferred for beginners, as they allow time to upgrade tank size before reaching maturity.

References

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