Loosing kribs fry

Hi,
The second spawned of my kribs was much successful than the first. And this
time I've decided to siphon 3/4 of the fry to their own tank. The tank is 30
gallons and has a sponge filter that was connected to a Power head, I think
part of the fries were lost because of it so I've connected the sponge
filter to an air pump. It seems that I continue on loosing them.
They are fed twice a day with frozen and dried food.
What am I doing wrong ?
10x

gizmo