[rayjay]

For me it wasn't even a consideration, and, I don't know if it is true.
I have timers set so that once I feel birthing date is imminent, I set the timers to turn off all pumps before lights come on in the morning, even the return, and just go with the air lines for water motion. Once the birthing occurs, if they need surface air they are free to do so or not as they choose.
When I transfer them to the rearing containers, I use only air lines for water motion, at least until they have grown a lot.
For me, I've ended up with floaters (that usually die although not all) whether or not I try to keep them from staying at the surface or not.
I've always assumed that the floaters have been affected by bacteria but don't really know for sure.
I change 100% of the water every two days, cleaning and sterilizing all surfaces of anything the water contacts.
My present batch of 103 barb fry had about 1/3 of them floaters by the fourth day and now 9 days in I've had to remove 17 of the dead that I'm assuming are from the floaters as the numbers of floaters has now decreased.
I've also noticed over the years, that as a male matures, the survival rate of the fry goes up. Anyone else noticed this?