Spaz
When fish breathe heavily this could be a sign that not all is right. Things to look for, high toxins such as ammonia and nitrite, very high nitrate as well. What is your pH? What if the temperature of the water? The higher temperature, the less oxygen it holds. Is your filtration setup properly so your water is being oxygenated? if the water coming back into your tank isn't creating any surface agitation whatsoever then you may find that you have not got enough oxygen in the water.
Is the fish eating okay? What about any other fish, are they behaving normally?
I would keep him in the tank where he is at the moment and just keep an eye on him. Hopefully everything will settle down and he will stop breathing heavily, fish shouldn't breathe heavily. What exactly are the test results for ammonia and nitrite?