If you vibrate your finger or a chop stick on the water surface, newly hatched fry will approach the vibration. What I do is vibrate in an area then slowly bring them to where I want to feed. Do it a few times and most of your fry should be in one place. . . . (male feed fry by vibrating his pectoral vigorously. Instinctively fry will approach the vibration).
Water quality IMO is the key. I have more success raising fry in many 1g tanks with 1-2 days 50-90% water change compared to my 40-50g tanks. I always assume 25 fry in a 50g would need less water change compared to 50 fry in a 1g. But the 25 get sick while the 50 thrive. So you need to do more water changes. Plants and pump/filter will help with water quality.
If I use big tanks, I do 20-30% every 2-3 days and total clean out every month (about 4 weeks).