How big do goldfish get ?

biggest recorded Goldfishes


A relatively small member of the carp family, the goldfish is one of the most commonly kept aquarium fish. Natural selection and selective breeding originating in China more than a thousand years ago has led to several distinct goldfish variations, differing in color, shape, fin and eye configurations. Nowadays, there exist roughly three hundred breeds. They are often a favorite pet for children and adolescents due to their relatively low maintenance requirements. As popular as they are beautiful, this type of fish can live up to twenty years or even more assuming proper care, housing and accommodations. The question is, however, how big can they get?

The myth

There is a myth circulating the elegant goldfish’s potential for size. Supposedly, a goldfish can grow as big as its environment lets it, very much like the magical dragons of the Song of Ice and Fire series. There are stories about 100 pound fish of the carp family. But not every carp fish is a goldfish. And naturally, the above is simply untrue when it comes to goldfishes. Goldfishes can’t reach a monstrous size, should one flush them down their toilet or release them into a river. Their size is determined almost completely by their genetics not by environmental factors such as their fish tank’s size. In fact, should a goldfish not have a large enough space to grow to its full potential, it is more likely that it will die before you even notice that the environment is not large enough to hold it. And even if it does survive in a too small and restrictive environment, other problems will likely surface, amongst them stunted growth, deformities and problems of various kinds with its scales and skin.

The facts

Goldfish sold as “tank suitable” will grow to roughly ten inches whereas those sold as “pond suitable” can reach a maximum of about eighteen inches. The vast majority of goldfish should be able to reach a size between eight and twelve inches, assuming reasonable conditions. And while there is truth in the notion that a goldfish typically does not outgrow its tank, this is not because the tank size impedes its growth. It is mainly because small tanks provide much poorer water quality compared to the larger ones. All in all, the poorer quality their environment has, the less will the goldfishes grow. And like it was stated earlier, the biggest factor to determine growth is the individual fish’s genetics. Better conditions give a goldfish better chances of getting big, in no way will they guarantee it.

All in all, assuming a goldfish has a good genetic potential for size and assuming it is kept in growth friendly conditions (good water quality and adequate quantity of food being chief amongst them) they will probably end up the same size, whether they are kept in a tank or swimming free in a river.

Meet the biggest recorded Goldfishes

“Simply amazing” was how Goldie, a 1ft. 3 inches long goldfish as of 2008, was described by a marine biologist. Some have claimed that Goldie is the largest goldfish in Britain, and the second largest in the world, behind a 1ft. 7 inches long goldfish currently located in the Netherlands. Another case was when in July 2010, a goldfish measuring 16 inches and 5 pounds was caught in a pond in Poole, England. According to Dick Mills, however, Secretary of the Federation of British Aquatic Societies (FBAS) such a size is “not that unusual”. According to him, there are probably even bigger goldfish out there, inhabiting ornamental lakes that people do not recognize as record holders.

In any case, whether such feats of size are unique or not amongst these cases, one can only feel amazement at the remarkable growth of these specimens. Their size could only be attributed to a combination of excellent genetics coupled with great care and living conditions.


To summarize, a goldfish will grow as big as the combination of its genetic potential along with its living conditions, nutrition and water quality chief amongst them, will let it. This maxes out at about eighteen inches, with the largest recorded goldfish having been encountered in the Netherlands followed shortly by Britain’s Goldie. Goldfish continue to grow as they age to the day they die, in small bursts. A small tank and other poor conditions will typically stunt their growth and limit their potential for size – if not outright kill them. In any case, however, one should definitely not fear that their goldfish will grow to a monstrous size should they be released in a river.