Twenty four hours after casting the eggs, you will notice an accumulation of tiny live creatures inside the hatchery ponds.
These are catfish frys.
Congratulations!
Your catfish hatched very well.
Depending on your type of pond system, you might need to run water, add aerators or do siphoning of wastes.
Also, depending on your pond type again, you might just wait and see them emerge after two days looking for first food.
Oxidation is the use of certain chemicals like salt, hydrogen peroxide, gentian violet etc to subdue the bad effects of decaying eggs in the hatchery.
Their application helps improve the water quality and therefore, less frys mortality.
Which means more frys, fingerlings and juveniles.
So, you can periodically pour in some oxidizing chemicals to help fry survivability.