Corydoras

Corydoras is a large genus of small, armored catfish native to freshwater streams, rivers, and floodplains across tropical South America, with the greatest diversity found in the Amazon and Orinoco basins. Members of this genus are characterized by rows of bony armor plates in place of scales, a body plan shared with their relatives in the family Callichthyidae. With well over 150 recognized species, Corydoras is one of the most diverse catfish genera and among the most popular groups of small freshwater fish, valued for peaceful, active bottom-dwelling behavior and social schooling habits.

• Small, stocky, arched body typically 5-7 cm depending on species
• Two overlapping rows of bony armor plates (scutes) running along each flank instead of scales
• Short paired barbels around a small, downturned mouth adapted for sifting substrate
• Rounded dorsal fin with a stiff leading spine; similar spine on the pectoral fins
• Coloration and pattern vary widely by species, from plain bronze or gray to bold spotted or striped patterns

The armored, plated body combined with barbeled downturned mouth and stocky arched shape identifies the genus, while precise species identification depends on color pattern and geographic origin.

Corydoras species inhabit slow-moving streams, backwaters, and floodplain pools throughout tropical South America, favoring soft substrates of sand or fine sediment where they can forage along the bottom. Water conditions vary by species and habitat, from clear, oxygen-rich streams to soft, acidic blackwater tributaries, generally within a warm tropical range of about 22-28°C. Many species are associated with leaf litter, submerged roots, or dense vegetation offering cover, and some are adapted to seasonally flooded forest habitats.

Corydoras are social, schooling fish that spend most of their time foraging along the substrate, using their barbels to detect small invertebrates, plant material, and organic debris in sediment. They periodically dash to the water's surface to gulp air, a behavior linked to an ability to use atmospheric oxygen via a modified gut, useful in oxygen-poor water. Breeding involves an unusual posture in many species, where the female cups the male's fin to catch sperm, then carries fertilized eggs to a chosen surface such as a leaf or glass to attach them, without further parental care afterward. Their constant substrate-sifting activity makes them important detritivores and scavengers within their native stream ecosystems.