In addition to killing organisms exposed to the air, there could also be other more serious issues. If these airpockets are being form a good distance away from the water outfall, it could be an indication that your water is supersaturated with oxygen. Its good to have high dissolved oxygen levels, but if your water is supersaturated, then embolisms can occur in the fish causing death (same sort of thing that happens to a scuba diver when surfacing too quickly...fish can get the bends too). If your trying to raise larvae, even saturated water can cause issues. Typically, until larvae and fry metamorphose into juveniles, the majority of their oxygen is absorbed through the skin (gills don't really kick in until metamorphosis). As such, their skin isn't as well adapted to breathing and osmoregulation, and levels of 99% oxygen saturation could give them serious issues. Older fish don't really have issues unless the water is supersaturated with oxygen.