Living things cannot live without air that has a reasonable level of oxygen content. Fishes, such as the goldfish and their carp relatives too, but as nature has it, these aquatic lifeforms can survive longer when oxygen is lacking such as when in murky water or when the water over them freezes during winter. As it turns out these fishes have the ability to make alcohol when oxygen level drops. To understand why this is happening, all you have do is to look at other animals’ (human beings included) response to the lack of oxygen.
When oxygen starvation occurs, carbohydrates continues to metabolize with little or no presence of oxygen and this process produces lactic acid which, when builds up, make a person experience burning sensation in the muscles. If this continues, lactic acidosis will occurs whereby pH of tissues drop, leading to failure of many organs that will eventually lead to death. Alcohol, on the other hand, is a survival-friendly substance which is easily purged from the body instead of piling up within to only destroy bodily functions. In this way, fishes with the ability to produce alcohol will be able to survived with low oxygen supply for months on end.
Obviously, the aquatic animals put in such predicament will not be healthy, but they will live until the situation cleared up. Of course, they won’t survive if, for example, the lake the fishes dwell in gets sealed up permanently and deprive them of oxygen, or you went away for years, leaving the fish bowl perpetually murky which also reduces the oxygen level they require to recover. While generally speaking, this nature’s marvellous mechanism will enable a goldfish that is low on oxygen to survive, it is not without its caveat.
You see, when alcohol is produced, the blood alcohol level in goldfishes and carps will be through the roof, having as much as 55 mg per 100 ml which will result in them unable to swim straight. In other words, they are pretty much intoxicated and swim wobbly, just as you would expect of a drunk person. Fortunately, there are no underwater fish-police to nab them for drink swimming or swimming under influence (SUI).
In any case, getting high on alcohol in order to survive doesn’t seem like a bad idea at all. Anyways, if you rear goldfishes or carps as a hobby and observed that are swimming as if they were drunk, well, they probably are. So, it is for the best interest of the fishes that you introduce more oxygen into the tank, or change the water.