Pygmy Cory

Geographical Origin & Biotope:

They are native to the Rio Madeira river basin, one of the main and massive southern tributaries of the Amazon River in Brazil. Their habitat is not the turbulent main river, but the small tributaries, quiet forest streams, marginal floodplain lakes, and residual pools rich in vegetation and tangled roots.

Taxonomy & Morphology:

They belong to the Callichthyidae family (armored catfish). Their morphology places them in the small and elite group of "dwarf" Corydoras, along with *C. hastatus* and *C. habrosus*. Unlike classic Corydoras with a stocky, 'dome-shaped', purely benthic profile, the Pygmy has a much more slender, tapered, and hydrodynamic shape, a clear evolutionary adaptation to a partially pelagic life (mid-water swimming).

Social Behavior:

The schooling behavior of *C. pygmaeus* is a unique spectacle. While other Corydoras haphazardly sift the bottom, a large school of Pygmies (15-20 specimens) will swim synchronized mid-water along the front glass, resembling a school of Tetras. If kept in insufficient groups (less than 6 specimens) they will fall prey to chronic terror, remaining perpetually hidden under wood until they die from stress.

Coloration & Sexual Dimorphism:

The coloration is sober but very elegant. The body is a shimmering light silver-grey, almost translucent, and is horizontally furrowed by a thick, sharp black stripe that runs from the snout, through the eye, along the entire flank until it widens slightly at the base of the caudal fin. Above this dark line runs a bright white stripe, surmounted by a thinner black line on the back. Sexual dimorphism is marked only in mature specimens: seen from above, females are noticeably rounder, broader (laden with eggs), and slightly longer, while males remain tiny, straight, and thin as pencils.

Tank Setup:

Their Lilliputian size (max 3 cm / 1.2 inches) allows them to be housed in very small tanks: a 40 cm (16-inch) nano-aquarium (30-40 liters / 8-10 gallons) can comfortably house a cheerful school. The substrate is the most critical parameter: it must strictly be very fine sand (not gravel, not sharp chippings, or ceramic quartz), as they love to sink their snout and microscopic barbels into the sand to sift it; a rough bottom will erode their sensors, leading to fatal oral bacterial infections. The tank must be richly planted. They love to rest balancing on the broad leaves of *Anubias* or *Echinodorus* or on wooden branches like little birds on a tree.

Diet & Feeding:

This is where many aquarists make fatal mistakes. Being Corydoras, they are expected to "clean the bottom" by eating leftovers. However, their mouths are tiny. A normal bottom wafer is too hard for them. Their diet must consist of very fine granules or tablets crushed into coarse powder before being put in. The absolute ideal for keeping them plump and in breeding condition is tiny live or frozen food: brine shrimp nauplii (which they will actively hunt swimming), microworms, and micro-daphnia.

Water Quality:

Originating from the clear tributaries of the Madeira River, they tolerate normal dechlorinated tap water well. They prefer a neutral or slightly acidic pH (6.0 - 7.5) and a stable, not too warm temperature (22-26°C / 72-79°F). Like all Callichthyidae (armored catfish), they possess the ability to breathe atmospheric air, swallowing air bubbles from the surface to absorb oxygen in the hindgut. You will occasionally see them dart upward, grab a bubble, and rocket back down: this is a completely normal and physiological behavior.

Compatibility & Tankmates:

*Corydoras pygmaeus* is the emblem of vulnerability. Its size literally makes it a "bite" (a snack) for medium-sized fish like Angelfish, Blue Gouramis, large Cichlids, or Barbs. Cohabitation must be limited to true nano-aquarium micro-fish: *Boraras*, *Trigonostigma espei*, *Pseudomugil*, Honey Gouramis, or *Otocinclus*. It is also one of the very few fish that is **100% safe for ornamental shrimp colonies** (Red Cherry / Neocaridina): their mouths are so tiny and their nature so peaceful that they will even ignore newly hatched shrimplets.

Aquarium Breeding:

In a well-fed school (ratio of 2-3 males per female) and after a cold water change that simulates the rainy season, they will begin a frantic reproductive dance. The females will glue the tiny eggs (1-2 at a time) in sheltered positions, such as the back of leaves or in hidden corners of the glass. The larvae are microscopic and need infusoria and paramecia in their very first days of life.

Risks & Diseases:

They are sensitive to high nitrates and the accumulation of dirt on the bottom (pathogenic bacteria and planaria), which will rapidly infect their barbels. Another risk factor is organic wasting: in aquariums with fast companions (like Danios), the food often does not reach the bottom or is too large, leading the Pygmies to literally fade away from malnutrition within a few months.