Mine hangs at the surface, and even makes slurping sounds as he tries to suck up floating cichlid pellets. Will even bat the Oscar out of his way to get at them.
When they are stressed by low oxygen or poor water they tend to burp up a big bubble from their gut and dart to the surface for new air. They are able to absorb some oxygen via their gut if the water quality is poor.
They do the burb and surface thing occasionally even if things are normal, but if they start doing it frequently, check the water / aeration thing.
Ian
