I've no idea about growth times, but with fry like this you will not usually see them until they are large enough to escape predation by the other fish in the tank.
I have had fry from various characins including pencilfish and cories appear, but in every case the fry have been larger enough that the other fish are not likely to consider them food. When the eggs hatch (and the egg(s) surviving predation is the big issue, not so much the fry) the hair-like fry tend to remain under cover among thick plants, in or under wood, etc, or with pencils sometimes among floating plants. The fry you/we see are those that were successful at surviving, and would have found microscopic live food. We see them when they are confident enough, and large enough to not be seen as food.