Corydoras duplicareus eggs

[e-mini]

Found some eggs from the above cory. How to check whether the eggs are fertile?

[celticfish]

Initially after laying, there is no visible difference between fertilized and unfertlized eggs.
As time passes the unviable eggs will turn white and eventually have furry white fungus growing on the outside of the shell.
This furry fungus will attack "good" (read fertilized) eggs too.
So its best to remove them.

Caveat, I have not bred corys before...
But from my research most breeders would remove them to a smaller tank.
This is so they can use menthylene blue to prevent the fungus from growing and spreading to the good eggs.

In your picture the egg in focus looks like its gone bad.
From the colour the rest still have a chance.

[aquanatix]

As celticfish mentioned,opacity of egg is the most obvious sign of fertility.
As with most egg laying fishes,infertile ones usually turn opaque-white then start growing furry white fungus! So long as the egg is still transparent or clear,you've got a good chance. Anyway,congrats on your spawn! Do update us with more pictures of them.