Only breed on healthy animals. Here are some points to look at:

Barbels, should be long, pointed and most often white or pale, NOT eroded. See Substrate on the Tank page.

Active fish with erect dorsal fins and fully spread tails.

Make sure you have both sexes!

No hollow bellies or sunken eyes.

Make sure you have both sexes!

If you can get fry from someone who has bred the species it´s often easier to breed them than wild caught specimens.

Usually use one female and two males. If you have more females and only one is interested in spawning, the other could be spending it's time eating all the eggs that the other is producing. The same goes if you have more than two males, the once that are not actively taking part in the spawning could go caviar hunting instead. If you are using only one male he might not be interrested, and I feel that using two males makes them more competitive, chasing the female and getting her in the right mood too.
Note that some males of territorial species such as C. barbatus and other large long-snouted species might fight and kill each other if the tank is too small.

Sexing

To be able to breed your fish you need to be sure that you have both sexes present! Might sound very basic but I've tried to spawn C. panda where the difference is not that obvious. I got a lot of eggs but none of them hatched since all three were females.

A sexually mature and conditioned female is always rounder than the male when seen from the side and from above. Some species, especially C. barbatus, can look like they are going to explode if you feed them well and they are carrying eggs.
When the fish are freshly imported they are NOT conditioned and it can be very tricky to tell the sexes apart. Buy 5-6 fish, if financial status allows, which usually gives you at least one of each sex.

A few of the species have very marked sexual dimorphism, where the male usually has the brighter colours, more markings in the ventral (goes for many of the species) and dorsal fins. This is especially true for the elegans-group (wedge-headed) and C. barbatus.

The ventral fins on the male is often more pointed and with a straighter rear edge. The female has a round rear edge. I will make some drawings later to show the differences.

In some species the male has a more pointed and elongated dorsal. This also goes for the pectoral fin, at least for C. cervinus, where there is very little difference in the other fins.

######### Identifying Male And Female Cory Cats

A good picture of male and female C. araguaiaensis at Planet Catfish

Conditioning

The easier species to breed, such as C. paleatus and aeneus, will often spawn if fed only flake food and pellets, but the trickier ones need live or at least frozen food.
You can condition males and females together and move the females that get round to a separate tank together with the males for spawning. You can also separate the sexes and feed the females very well without the risk of them spawning when you are not prepared. (I've had a single female C. sp. "Peru gold-stripe" spawn on her own though.)
I usually condition my fish with the following live food: grindal, white, and micro worms, also newly hatched brine shrimp.
For frozen I use white and black mosquito larvae (I'm allergic to the red so I can't use them anymore which is a shame), cyclops, adult brine shrimp, and my own shrimp mix.
Apart from the above I use a pellet that's used in professional reaaring of salmon.
Simply stuff as much food in the tank as they eat within half an hour. If you have a bare bottom breeding tank it's easy to see when they have finished eating or if you should sifon the leftover food out. Feed several times a day if possible, and of course change water to keep a high water quality.

Triggering

Often the biggest problem when it comes to the problem species. You could feed them well and the female looks like a meat ball, but no spawning. There is something missing to trigger the spawn.
Some, like C. aeneus and C. paleatus, you only have to feed well for them to spawn. Other species need a lot more tweaking before they will spawn. All of the species come from a part of the world where there are marked rainy and dry seasons. So trying to simulate as many of the differences as possible is a good idea when you want your fish to spawn.
One of the easiest is to change a large portion of the water with fresh, cold water so the temperature is lowered rather drastically. You can also add peat, increase/decrease the flow/air in the tank. I've written an article that you find below about simulating the rainy season in a tank. I've tried to list all the different triggers I have found in literature and on the net.
The article also outlines how you should set up the tank for successful spawning.

Simulating rainy season in your tank, by me.

Spawning

The spawning itself is described in the articles below.

Cory Corner Breeding Corys, by Paul Schuman (Aqualink Column)

JAWS Breeding Info - Corydoras sp.

Keeping And Spawning Corydoras Catfish Petfish.net

Hatching

Can be a tricky part. This is how I do it and it often gives me 90-95% hatch rates even from tricky species such as C. barbatus.

I always take out the eggs. Some parents will eat the eggs when they have finished spawning. It's also harder to use methylen blue in a tank, it's a very strong dye. The fish usually spawns several times once they have started. Taking out the eggs usully never bothers them. I've taken out C. cervinus eggs from a big lump of Java Moss while they were spawning on the other side of the lump!

Put them in small containers (2 l/0.25 gal) with water from the tank. Use HEAVY aeration. I use the equivalent of one small air pump with one outlet for one or maximum two of these containers.

Add one or two drops of methylene blue to the water to reduce fungusing.

Take out 80-90% of the water daily and add back water with the right temperature using an air hose with a restriction so only about one drop a second drops in to the container. If you have problems with your tap water use perhaps 50% RO-water (make sure the hardness don't get too low).

Raising fry

Raising Cory Cat Fry

Odling av malar med kapitel om pansarmalar