Corydoras pygmaeus (pygmy cory)

Taxonomy:
Corydoras pygmaeus which is most known as the pygmy cory belongs to the Corydoradinae subfamily, Callichthyidae family, and Siluriformes order.
Distribution-Habitat:
The species is native to South America (Rio Madeira in Brazil). In general, corydoras occur mostly in shallow, clean or muddy pools, in margins of ponds and streams covered with plants, stagnant waters with soft bottoms (sand) but also inhabits slightly running waters. The water has a high amount of tannin due to the decomposition of leaves and wood that makes the water tea-colored (an indication of soft and acidic habitat). Furthermore, Corydoras occur in seasonally flooded rainforests.
Description
Corydoras pygmaeus have a short and rounded snout with six barbels around the mouth that are used as tactile organs to obtain physical information about objects, to find food and in courtship. The color of their body is grey-green with horizontal black stripes from the head to the caudal peduncle.
Even though Corydoras breath with their gills, they also breathe air from the surface intestinally. The surface air gets stored by the corydoras in the thin walls of intestine’s posterior part. As a result of the modification and vascularization of the posterior intestine, makes the organ well suited for gas exchange.
The species is one of the smallest corydoras with an average size of 1 inch (2.5 cm) with females being insignificantly bigger than males and with a larger abdominal region. The species have a lifespan of 5 years, but with the right conditions they may live up to 7 years or more.
Habits:
It’s advised to keep the species at least in a group of 5 corydoras and more due to their schooling behavior. In nature, Corydoras usually live in shoals of 20-30. Because of their peaceful temperament corydoras are compatible in community tanks with tranquil and small species such as tetras.
Because of the natural habitat of Corydoras pymaeus should be kept in soft acidic water. A pH between 6.4-7.0, with a temperature between 22-26 Celsius, and a hardness between 50-150 mg/l, suits the species.
An aquarium with 51 liters of water(13,5 gallons) is suitable for a shoal of 10-11 Pygmy Cories. Although plants are not usually a characteristic of corydoras’ habitat, a planted aquarium has many advantages for the owner and the fishes. The substrate must be soft and the decoration without sharp points for the avoidance of injuries of the corydoras’ sensitive barbels.
Many beginners use the species to clean the bottom from the leftovers of other fish in the aquarium but like all animals need a proper diet. Some even think that corydoras are coprophagous which is a myth. Corydoras are omnivorous and can eat prepared food (sinking pellets) and small live-foods such as brine shrimp, bloodworms, daphnia, etc. In nature, their diet consists of worms, crustaceans, and plant matter.
Breeding:
In their natural habitat reproduction occurs in the rainy season (change of chemical and physical quality of water). In the aquarium, you can trigger breeding by changing a large amount of water (20-50%) or daily water changes (10%) and lower the temperature a bit (2-4 Celsius). One way to reduce the heat is by cooling water changes (recommended). Another way to reduce the heat is with a heater. I have to mention that Lowering the temperature in community tanks can cause negative consequences on other species. Furthermore, the addition of a varied diet of high quality aids the reproduction of the species, as well as raising the amount of the food than the usual portion.
During breeding conditions, they chase each other around the tank with the male displaying his abdomen for the female. Then the female corydoras’ mouth will adjust over the male’s opening to collect the sperm, forming the characteristic T-position. The sperm travels to the eggs through the female’s intestines. After the fertilization of the eggs, the female releases and deposits the eggs in a safe location (rocks, glass, leaves of plants). The action is repeated many times by the corydoras.
Corydoras pygmaeus produce about 100 eggs in one day. The young hatch after 3-5 days with a temperature of about 22 Celsius (the hatching period of the young is affected by the water’s heat) and for 2-3 days feed on the yolk sac, so in that period they don’t need food. After the consumption of the yolk sac, they search for food on the bottom. You can feed the young three times per day with brine shrimp, micro-worms, powder food, etc.
For the survival of the young, the species is best to spawn in a breeding tank with shallow water. When the whole process ends, remove all the adult corydoras. You can also place the offspring in breeding traps or plastic containers. Furthermore, the addition of an air pump helps the flow of water and prevents the infection of eggs from fungus. You can also use fungicides for a better outcome.

Group of Corydoras pygmaeus (Pygmy Cory) in planted tropical fresh water aquarium
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References:

  1. David Alderton 2005, 2008, Encyclopedia of aquarium and pond fish, Published in the United States by DK Publishing, ISBN 978-0-7566-3678-4
  2. Immunohistochemical and ultrastructural evidence of functional organization along the Corydoras paleatus intestine 2016. Retrieved from https://www.researchgate.net/publication/290221812_Immunohistochemical_and_ultrastructural_evidence_of_functional_organization_along_the_Corydoras_paleatus_intestine
  3. Corydoras Pygmaeus. Retrieved from https://www.seriouslyfish.com/species/search/corydoras+pymaeus
  4. Corydoras Pymaeus. Retrieved from https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=164319#null

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