Pygmy Cory (Corydoras pygmaeus)
Family: Callichthyidae, Subfamily Corydoradinae
Common Name: Pygmy Cory
Origin and Habitat: Endemic to the Rio Madeira system in western Brazil. Occurs in small creeks and flooded forest, in large groups around aquatic or marginal vegetation and tree roots.
Compatibility/Temperament: Very peaceful dwarf cory species that is suitable for any aquarium with small, peaceful fish. Must be in a group, at least six but will be much more at ease and healthier with nine or more.
Pygmy Cory Diet
Feeds mainly from the substrate so sinking foods such as tablet, disk and pellets are mandatory; frozen bloodworms or small live worms are relished. Browses plant leaves, wood, and rocks continually looking for tidbits of food. Suitable substrate food must be provided; these fish will not survive on left-overs from upper-feeding fish.
Around 1 inch, sometimes attains 1.3 inches.
Minimum Tank Suggestion
5 gallon for a small group.
Water parameters for Pygmy Cory
Soft to moderately hard (hardness to 15 dGH but preferably below 8 dGH) acidic to slightly basic (pH to 7.4) water, temperature 22-26C/71-79F. Long-term it does better in soft, acidic water.
Described and named by Knaack in 1966, this is one of three common "dwarf" species of Corydoras; the other two are Corydoras hastatus and C. habrosus, and the behaviours are very similar. All Corydoras species tend to swim throughout the tank, browsing wood, rocks and plant leaves for food, but these species spend considerably more time off the substrate than most of the larger species. They may sometimes join groups of small characins and shoal with them. It is not coincidence that the attached photos all depict this fish mid-water.
The tank should have a smooth sand substrate; gravel is not recommended for this species. Pieces of bogwood are appreciated as browsing areas and for shelter, and aquatic plants. Floating plants will help to shade the light, as this species prefers subdued lighting.
When viewed from above, females are rounder than males, and sometimes slightly larger.
The Corydoras are quite sensitive to water parameters and quality, and highly intolerant of salt, chemicals and medications. Signs of stress usually begin with rapid respiration, then lethargy (often just "sitting" on plant leaves, wood or the substrate respirating heavily, sometimes near the surface) and sometimes rolling onto one side. At such signs, a partial water change of at least 50% with a good water conditioner should immediately be made, and appropriate steps taken to remove the cause. Any sudden fluctuation in water chemistry or temperature often induces shock, causing the fish to "faint" and fall over on its side. Corydoras introduced to new aquaria will settle in better if the tank is established; corys do not adjust well to a new aquarium with still-unstable water conditions and fluctuations. When introduced to a relatively-new aquarium or one with water parameters outside the preferred range, this species will sometimes die within a few weeks.
The dorsal, pectoral and adipose fins are each preceeded by a spine which is actually a hardened and modified ray; the pectoral fin spine can be "locked" into position by the fish; care must be taken when netting corys not to entangle these spines, which can also give the aquarist a nasty jab. They are believed to be a defense adaptation, to lodge the fish in the throat of a predator.
All species in the genus will periodically and fairly regularly swim quickly to the surface for a gulp of air. The fish swallows the air and blood vessels in the hind gut extract oxygen from the air; it is then expelled through the vent the next time the fish breaks the surface for another gulp of air. This adaptation is believed to have evolved so that the fish can survive in poorly-oxygenated water such as drying pools during the dry season. It is however essential to the fish's well-being that it regularly swallows air.
The name of the genus, which was erected by B.G.E. Lacepede in 1803, is derived from the Greek cory [= helmet] and doras [= skin, incorrectly used here for "armour"]; it refers to the dual row of overlapping plates (instead of scales) along the body, comparable to a suit of armour. The species epither pygmaeus is the Latin for dwarf.
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