posibly around 1 million!
if im thinking correct and the tank is a 2 foot by 1 by 1
then id say as many as all your fish could muster ( more then you would ever want or need)
its once they hit juvy stage that you would have a problem but i reckon that would sort itself out ( survival of the fittest and 2nd fittest and 3rd lol)
I kept 250ish in a 2x1x1 for 3 months, just gave them 10% water change every day to ensure good water quality, had no deaths at all. but now have 3 fry tanks for different types of fry.
Keeping up with water changes is one thing, but your fish need room to live and to swim. I would say even 100 would be too many in a ten gallon tank. You're going to start stunting the growths of your fish if they don't have enough room. In a standard ten gallon, I wouldn't put more than twenty fry in the tank at two month's growth size.
I would say it depends on how large you are going to raise the fry in the tank until, with regular water changes and good filtration i would say you could easily have about 30-40fry in there if you are just raising them to be larger enough not to fit in other fishes mouths.