Swim Bladder Disorder is a condition that affects constipated goldfish; the build-up of food causes the stomach to press against the swim bladder so that the fish loses control of its buoyancy. They will lie sideways and may be unable to stay submerged; sometimes they try to jam their bodies underneath stones, but if that doesn't work they just float to the surface and lie there (or, sometimes, sink to the bottom and lie there).
They can survive on the surface, and can recover with time - they may get better after about three days' fasting. It's easy to overfeed goldfish; their stomach is about the same size as their eye, and giving them any more than this is likely to cause problems.
Colin is the sort of name you give your goldfish for a joke.
Pet goldfish can live for 25 years.
'Goldfish' was the American code-name for France during the Second World War.
Goldfish memory isn't a few seconds long. Icthyologists have known this for a long experiments, goldfish were trained to push a lever to earn a food reward; when the lever was fixed to work only for an hour a day the fish soon learned to activate it at the correct . A number of studies have shown that farmed fish can easily be trained to feed at particular and places, in response to an audible signal.
Goldfish don't swim into the side of the bowl, not because they can see it, but because they are using a pressure-sensing system called the lateral line. Certain species of blind cave fish are able to navigate perfectly well in their lightless environment by using their lateral line system alone.
Pregnant goldfish are not called ‘twits’ - goldfish lay eggs.
The eyes of the celestial eye goldfish are literally bigger than its stomach.