"Pop eye can also be caused by gas bubble disease as a result of oxygen super saturation (excess levels) of the water with the gas, nitrogen. How does nitrogen lead to super-saturation of oxygen? These are elements, completely separate from each other. Super saturation occurs whenever the pressure of a gas in the water is higher than the pressure of the same gas in the surrounding atmosphere no, supersaturation occurs (in this case) when water holds more of something than it normally would. you can put a certain amount of liquid sugar into boiling water, but the same amount of sugar could not be held in liquid form by cold water. when you cool down that boiling water, the cooler water is now supersaturated. While the tap water may in fact be supersaturated as compared to the pressure found in the aquarium, you would have seen lots and lots of tiny bubbles coming out of the end of the python, and bubbles would have been left on the glass when you filled the tank. , whereby the difference in gas pressures causes the gas to get pulled too quickly out of the fish's bloodstream, leaving behind gas bubbles seems to me the excess gas would evaporate out into the atmosphere almost immediately as it entered the aquarium. the fish have nothing to do with it unless they are sitting right in the flow of completely new water and 'inhaling' the excess gases. Or they would have to be in a pressurized aquarium. The other symptoms of this are the appearance of bubbles under the fish's skin. It's caused by excess oxygen in the water, particularly from filters that blow air directly from outside to inside the tank, and from pressurized tap water that did not get mixed. It is not caused by excess oxygen - air pumps and pressurized tap water will only contain the same amount of oxygen that is already in the air - about 21%. Air pumps do not selectively pull oxygen from the air. Tap water in fact may contain even less oxygen than is in the air because of the addition of chlorine, which will try and gas off as soon as it can. Any oxygen that cannot be absorbed by the water (depending again upon temperature) will simply rise to the surface and gas off"