Make sure the food is not moldy; either as dry food or aged hydrated pellets. Early onset mold on pellets is hard to notice. Do not store hydrated pellets longer than 48hrs even 36hrs to be conservative. The deaths in 1st 2 weeks were very likely handling strssors. Deaths in first two weeks are almost always handling problems. Your few subsequent deaths 'could' still be due to handling, likely from the source.
The only time I have seen the strange behavior you describe is when some YP were over laden with eggs. Gulping air is not an issue. Eating too many floating pellets could be a possibility, but this would be extremely rare. If the problem was water quality lots more fish would be dying, not just a casual death.
Last edited by Bill Cody; 06/13/19 04:39 PM.
