had this problem too, the ornate lost buoyancy, first the he was on the ground with head on the substrate while half his body was floating, then after 5 hrs he lost total control floating all-around.
what i did was net him, and placed the net 1-2 inch deep in the water for 24hrs in the community tank, this prevented him from floating all around the place, and if needed he just needed to raise his head to gulp air, this can also be done on a quarantine tank with water 1-2 inch deep depending on the size of your bichir. then i just let him pass the air by him self, i released him after 40hrs when he regained his buoyancy.
in my case, i think he got air due to eating rotting fish fillet after i failed to remove uneaten peaces, rotting meat produces gas when eaten.
hope this helps as an alternative to physically handling them.
