Hydrolycus armatus is the largest of the Payara species and shares the extraordinary fang morphology of its congeners — the massive, curved lower jaw fangs that lock into rostral pockets when the mouth is closed are even more pronounced in large adult specimens. Found in fast-flowing rivers of the Amazon and Orinoco basins, it is an apex predator that can reach 90 cm in large wild individuals and is one of the most formidable freshwater piscivores in South America.
In captivity, H. armatus requires conditions as demanding as H. scomberoides: very large, highly oxygenated tanks with powerful flow, pristine water quality, and a live or freshly dead fish diet initially. It is sensitive to water parameter fluctuations and requires stable, soft, warm water to remain healthy. Weaning from live prey to dead or prepared food is a major challenge and should be approached with patience and variety.
Hydrolycus armatus is even more rarely available than H. scomberoides and its larger maximum size means the tank requirements are correspondingly greater — minimum 4000 litres for a specimen of any size. This is unambiguously a public aquarium or dedicated specialist fish. Under the right conditions it is a breathtaking display animal.
