Breeding Corydoras
Hello A...
Well, I can tell you that Corys prefer sand as a substrate. A fine, polished gravel will also work. The substrate should be dark, because these fish are light senative. Lower light in the tank, makes them feel safe.
Corys like the tank water a little warmer, 77-78 degrees is optimum. They require pure water conditions, so changing out half the water in their tanks every week will keep the water chemistry stable.
The hard part is maintaining a neutral pH. I've had a number of eggs laid in my Cory tanks, but my pH, at 7.4 is a little alkaline. So, I've never had any eggs hatch. The eggs are also a nice snack for any fish with a mouth large enough to eat them.
Numbers are important too, but the fish don't necessarily have to be the same species. I stock 1 for every 5 gallons of tank volume and a minimum of 5. More is better. Some of my Cory tanks have several species in them.
If you can accomplish the above, your chances of having little ones is pretty good.
B