Danios are broadcast spawners, which mean you need a large school of them (at least 20+) to get any sort of success. They have no parental behaviors. They simply shed sperm and eggs into the water, which drift down to the bottom of the tank to the gravel. If not protected, the eggs will be eaten by tankmates and the parents themselves. I do not know of anybody who has ever breed these guys in personal aquarium tanks, but I know research facilities do breed these and other danio species in large schools.
Your two danios, if male and female, are probably doing mating riturals or just testing each other for dominance. I doubt you will have any fry raised, especially if you have bottom feeders like loaches and cories that will suck up the eggs. I know the book -You and Your Aquarium- by Dick Mills has suggestions on how to set up breeding facilities for broadcast spawners.
~~Colesea