Iridescent Shark Care Guide - Size, Diet & Aquarium Facts

The Iridescent Shark is a sleek, high-bodied catfish with a blue-grey to silver body, a darker back and a striking metallic sheen that gives the species its common name. Its pointed head, forked tail and prominent barbels contribute to its shark-like appearance, although it is a true freshwater catfish rather than a marine shark.

Young fish are especially attractive, displaying bright silver sides and dark markings on their fins. As they mature, they lose some of the dramatic juvenile contrast and become powerful, streamlined fish capable of reaching an extraordinary size. Their large eyes and sensitive barbels help them navigate and locate food in turbid water.

In the wild, Iridescent Sharks are active open-water swimmers and often travel in groups, particularly when young. They can be nervous and prone to sudden bursts of speed, and their instinctive movements become increasingly difficult to accommodate as they grow.

This species is an important food fish throughout Southeast Asia and is widely produced in aquaculture. Its impressive adult size is often underestimated because fish sold in shops are usually juveniles; a small specimen can eventually become a fish more suited to a public aquarium or very large specialised facility than a typical home tank.

Iridescent Sharks are native to large rivers of mainland Southeast Asia, especially the Mekong and Chao Phraya basins in Thailand, Laos, Cambodia and Vietnam. They inhabit broad, flowing freshwater channels and floodplain environments.

A full-grown Iridescent Shark requires a public-aquarium-scale enclosure rather than a conventional home aquarium. A practical minimum for a group of juveniles is around 2,000 litres, but this is only a temporary stage; adults need many thousands of litres and a tank or indoor pool at least 300 cm long, with substantially greater length and width preferred. Use powerful, reliable filtration, strong oxygenation and generous open swimming space, while securing the enclosure because startled fish can injure themselves by crashing into covers or equipment. Keep decor sparse and smooth, with rounded gravel or fine sand, sturdy roots and rocks positioned around the perimeter rather than in the swimming lane.

Up to approximately 130 cm (51 in) in the wild. Females are generally heavier-bodied than males, while captive specimens are often smaller because of limited space and long-term husbandry constraints.

Iridescent Sharks are omnivorous and become increasingly willing to accept a broad diet as they mature. Offer a high-quality sinking pellet or carnivore food supplemented with prawns, mussel, earthworms, insects and occasional fish-based foods, along with suitable vegetable matter such as shelled peas or blanched greens. Juveniles can be fed small, appropriately sized foods, while adults should receive measured portions to prevent obesity and excess waste. Avoid relying on live feeder fish or fatty mammalian meats.

Suitable companions must be large, peaceful and robust enough not to be swallowed or injured by an adult Iridescent Shark. Depending on the scale of the aquarium, possibilities may include large peaceful barbs, silver dollars, giant gouramis and suitably sized, non-aggressive large catfish. Do not keep them with small fish, delicate species or fin-nippers, and avoid aggressive cichlids and territorial predators. Because of their adult size and nervous swimming behaviour, finding genuinely suitable long-term tankmates is difficult in a domestic aquarium.

Iridescent Sharks are not realistically bred in ordinary home aquariums. In nature they undertake seasonal migrations to spawning areas, and captive reproduction has mainly been achieved in commercial fish farms using controlled conditions and, in some cases, hormone-assisted techniques. They are egg scatterers, with females releasing large numbers of eggs that are fertilised externally. Successful breeding requires very large facilities, mature broodstock and carefully managed water movement.

Mature females are usually deeper-bodied and heavier than males, particularly when carrying eggs. Males tend to have a slimmer profile and may show stronger contrast in their breeding coloration, but sexing young Iridescent Sharks visually is very difficult.