
I think it's air, as the fish is very buoyant and struggles to maintain its orientation. However, there's an outside chance that it could be an infection; several Steatocranus casuaris in this tank have died recently, and some have exhibited bloat and popeye-like symptoms.
Was considering trying to remove the excess gas or liquid with a hypodermic needle, but feared the cure may be more dangerous than the disease. The timely advice of the veterans on this forum would be much appreciated.
Thanks,
Dinyar