Dwarf Cory (Corydoras hastatus)
Family: Callichthyidae, Subfamily Corydoradinae
Common Name: Dwarf Cory
Origin and Habitat: The Amazon and Paraguay river basins; reported from the Rio Parana. Occurs in small creeks and flooded forest, in large groups around aquatic or marginal vegetation and sunken branches and 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.
Dwarf 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, 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 gallons for a small group.
Water parameters for Dwarf Cory
Soft to moderately hard (hardness to 15 dGH but preferably below 8 dGH) acidic to slightly basic (pH to 7.2) water, temperature 22-26C/71-79F. Long-term it does better in soft, acidic water. Prefers quiet water without strong currents.
This species was described and named by Eigenmann & Eigenmann in 1888; it is one of three "dwarf" species that share similar behaviours, the other two species being Corydoras pygmaeus and C. habrosus. All Corydoras species tend to spend time swimming 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. C. hastatus spends most of its time mid-water, stopping to rest on plant leaves; it will frequently shoal with small characins, especially those that have similar colouration and body patterning.
The tank should have a dark or natural-coloured fine sand substrate, smooth and not sharp-edged. Pieces of bogwood are appreciated as browsing areas, 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 epithet hastatus is the Latin for spear-shaped.
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