Basically unless you remove the parents and any other fish which could posibly eat the fry and eggs (which is basically most fish), you are highly unlikely to be able to successfully breed and rear any danio fry at all- the fry are very vunerable for a long time.
Ideally you need;
a. A cycled/established tank of at least 10-15gals, sub-tropical temps (19-23 dgrees) are best for breeding danio's in my experience.
b. Some nice healthy plants with small and dense leaves to help create a densely planted area in the tank.
c. Excellent water quality and lots of water changes and good food for the adult danio's (frozen foods like bloodworms, daphinia, krill etc are great) and liquid fry food for the fry like Liquifry.
d. Fine sand substrate is best since its easier to keep clean and see the fry on.
When the adults have finished spawning you should remove them from the tank- its up to you really when exactly you do it though. Dense planting is good as its helps protect the eggs from other fish including the parents after they have finished spawning. They may spawn many times so you may want to leave them there for a couple of days during their spawning. I can't remember exactly how long it took for me for the eggs to hatch, i think it was around a week before i noticed any fry in the tank.
The fry are really tiny! They are much smaller and thinner than newborn guppy fry and are practically see-through, and tend to swim around the bottom to middle section of the tank- you'll need to keep on looking everyday very hard to see them. Liquid fry foods are best since the fry are so tiny (most dried foods are too large for the fry), you need to stir the fry food up a bit in the water otherwise it'll just sink in a big glob to the bottom of the tank.
For me i got around 100-150 fry for a single pair of pearl danio's, and it took around a year for the fry to be fully grown. Most of the fry will end up dying when tiny (its quite normal for them to do so apparently) , so you don't need to worry too much about the amount of fry you'll end up having to raise- out of the 100+ fry i had 25 of them grow to adulthood in the end.