Newly hatched brine shrimp (1st 12 hours) still carry a yolk sac packed full of nutrients which specifically aid growth. If you 'wash' the brine shrimp in fresh water the amount of salt is negligible and they are the perfect size for most fry.
When I use a fresh hatch, any I have left (if not enough to freeze) I drop in my community tank, great fun watching my 3" Angel trying to eat as many as he can before the neons get them - like watching an elephant trying to eat peas one at a time!