Do newly hatched fry need to surface for air?

[alunjai]

My fry are 3 days old and half of them sunk to the bottom (maybe feeding on bbs) and I was wondering if they need to swim to the top for air like the adults?

[Myates]

Not at that young of an age - their labyrinths start to develop roughly around the 7 week mark. Either lots and lots of live plants or a sponge filter will help give them the oxygen they need at that age.