Breeding Corydoras & Related Species.

Text by Paul Barrow
Images of Corydoras paleatus by Brian H Risbridger
Images of egg depositing by Paul Barrow

This article, specifically for Corydoras species, also relates to Aspidoras, Brochis & Scleromystax, all of which breed in a similar manner.
See article on sexing Corydoras; this is a guide for identifying the gender of a single fish. When Corydoras are in groups, it is easy to tell females at a glance because they are bigger and more robust than the males - assuming they have been brought up together!
Breeding these fish seems to depend on species, some like Corydoras pygmaeus will spawn at regular interval, while other seem to have evaded all attempts to induce them to spawn. Very young Corydoras of only a few months old will spawn, but this usually results in mostly infertile eggs, success increasing with age.
The first essential is a least a group of one female to at least, two males, bigger groups equating to a more successful outcome. These should be condition on a good, mixed diet such as whiteworm, grindle worm, brine shrimp, and good quality dried & frozen foods. Try to avoid aquatic live foods such as Bloodworm & tubifex because of the associated risk of introducing pathogens.

When the group is conditioned, the males will start to chase a female -

- during this time she will deposit a small clutch of eggs into a pocket formed by her pelvic fins.

 Once ready to spawn, the female rests on the bottom and chooses one of the accompanying males. She approached the male's side, her barbels are grasped by the male's pectoral spine - this is known as the 'T' position. He then starts to quiver and released milt, which the female takes in her mouth.







There are two schools of thought as to what happens next.
Theory (1)
The female cleans a spawning site for the eggs, depositing sperm at the same time. When the eggs are stuck to the spawning site, they are fertilized by the layer of sperm.
Theory (2)
The milt is swallowed and passes through her digestive system and in expelled through her anus directing onto the eggs between her pelvic fins. Theses are then deposited onto the cleaned spawning site.
Both theories have evidence to support them; it's more important to scientist than aquarists to decide if one, or both theories are correct.
 














The  female (1) opens her pelvic fins, (2) presses the sticky eggs on to the site, (3) leaves the eggs behind
The eggs are very sticky and stay in place for up to a week, the developing fry clearly visible through the clear shell. Newly hatch Corydoras are like small glass balls with a tail. They need the finest of foods; infusoria or liquid egglayers fry food such as Liquifry, before moving on to microworm and brine shrimp. At this stage they are minute replicas of their parents, usually with two vertical, black bands. Many breeders insist they need calcium during the first few weeks and introduce small amounts of chalk to the aquarium. Once past the brine shrimp stage they are much easier to feed, taking the same foods given to their parents, which should be chopped up or crushed to a suitable size.