If you have an extra free tank, separate the large and small ones. Though the small ones eat like crazy, for some reason they will remain small if not separated.... maybe it's the stunting hormones, IDK. I didn't separate mine and the difference was 2.5cm - 0.5cm.
I often keep 6 - 12 fry under 2cm (less if I want to boost growth) in 1g (flat/shallow containers are better than normal tanks) but give them 2x 30-50% daily, feed 3 x a day. But once they reach 2cm, they have to be moved or reduced. Otherwise you might get problems.