Scleropages formosus

Lore & Background

The Asian arowana belongs to the order Osteoglossiformes, a lineage of bony fishes whose fossil record stretches back to the Cretaceous. Members of this group possess a suprabranchial (accessory breathing) organ that allows them to gulp air at the surface, a trait shared with their distant relatives the lungfishes and bichirs. In the wild, S. formosus occupies the upper trophic levels of tropical river systems, feeding on surface insects, small fish, frogs, and even small birds or mammals that venture near the water's edge. Its powerful, hinged lower jaw and rapid strike make it one of the most effective surface predators in its range.

In the aquarium trade, the species is prized for its size, longevity, and dramatic behavior. Well-maintained individuals can exceed 70 cm and live well past 15 years, making them a long-term commitment. Their reputation as powerful jumpers—capable of clearing tank lids to seize prey or escape—is well documented in keeper literature. Color morphs, particularly the red-gold and green-gold varieties, have driven significant market value, and selective breeding programs in Southeast Asia have produced a range of hues from pale gold to deep crimson.

Conservation pressure is substantial. The IUCN lists S. formosus as Endangered, citing loss of riverine habitat from damming, logging, and agricultural runoff, compounded by sustained collection for export. Several range states have implemented size limits or seasonal collection bans, and CITES Appendix II listing provides an additional layer of trade regulation. Captive breeding, while widespread in the aquarium industry, does not yet offset wild-population declines in all parts of its range.

Reader's Guide

Tank size: Scleropages formosus is a large, active species. Published aquaculture and keeper-consensus sources recommend a minimum of 1,500–2,000 L (400–500 US gal) for a single adult, with length being the critical dimension. A tank shorter than roughly 1.8 m will restrict natural swimming and increase stress.

Cover: This is non-negotiable. The arowana is a documented jumper and can clear unsecured lids easily. Use a tightly fitted glass or acrylic lid, or a mesh-top enclosure with fine enough gaps that the fish cannot slip through. Multiple keeper reports cite escape incidents even from well-established fish.

Water parameters: Tropical freshwater. Temperature in the mid-20s °C range (approximately 24–29 °C) is the commonly cited band in aquaculture literature. pH slightly acidic to neutral (roughly 6.0–7.5) reflects natural tannin-stained river water. Ammonia and nitrite should be kept at zero; nitrate below 20 mg/L is the general keeper-consensus target.

Feeding: Carnivorous. A varied diet of appropriately sized fish, crustaceans, and occasional invertebrates is standard in published husbandry guides. Avoid overfeeding; obesity is a common issue in captive specimens. Transition from live to frozen/processed foods is recommended to reduce pathogen load.

Common mistakes: Underestimating adult size; inadequate lid security; keeping with small tankmates (they will be consumed); poor filtration for the bioload of a large predator. Source: general aquaculture literature and experienced-keeper consensus; verify specific values against your local water-chemistry guidelines.

Did You Know?

• Scleropages formosus possesses a suprabranchial (accessory breathing) organ, allowing it to gulp atmospheric air at the surface—a trait shared with other osteoglossans and distantly related to lungfish air-breathing.
• The species is a well-documented jumper: individuals have been recorded leaping well above the water surface to capture aerial prey or escape, a behavior that makes secure tank lids essential in captivity.
• Osteoglossidae, the family to which the arowana belongs, is one of the oldest surviving lineages of bony fishes, with a fossil record extending into the Cretaceous period.
• Selective breeding in Southeast Asian aquaculture operations has produced a wide spectrum of color morphs—from pale gold to deep crimson—driving significant commercial value in the ornamental trade.