Category: General Fish Health

biggest recorded Goldfishes

How big do goldfish get ?


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.

Most Effective Ways to Safely Get Your Fish to a Healthy Weight

I got an interesting question from a reader, Brooke, she asked my advice on how to help an underweight fish get back to a healthy weight. I’ve done this with my rescue Betta, Bub, and I think that this is a very important and often overlooked aspect of fish-keeping. The obvious answer would be to feed the fish and feed it a lot, however, I disagree with this method for a few reasons. Many fish like Bettas or African Cichlids, especially those from Lake Malawai, are very prone to constipation even when healthy, and throwing a bunch of food at them at once might only make things worse.

There are numerous reasons your fish could be underweight, most likely they stopped eating due to stress or illness or injury. Sometimes you’ll buy a fish that’s underweight or sometimes you’ll just get an incredibly picky fish that is reluctant to eat.

In my experience, the best way to help a fish get back to a healthy weight and regain it’s physical strength as well as regaining healthy immune system function consists of three main things:

  1. High quality food (New Life Spectrum, Omega One, etc.)
  2. Vitamin Supplement like Vita-Chem or Seachem’s Nourish
  3. Seachem’s Garlic Guard

And sometimes feeding a food like San Fransisco Bay Brand’s Beefheart Plus is effective, especially with carnivorous fish like Bettas or Puffers. Obviously if you’re dealing with a herbivore that doesn’t digest protein very well like Malawi Cichilds I would strongly advise not using Beefheart as it’s extremely high in protein.

High-Quality Foods:

First though, let’s briefly go over why you should be using a high-quality food even though it’s pretty self-explanatory. Higher quality foods contain more natural ingredients, more vitamins, they’re easier to digest because they use less unnatural fillers and the list goes on. If you want to learn more about fish food specifically, click here!

It’s very important than when feeding you should always aim for smaller feedings throughout the day, especially with an underweight fish. I find that this helps prevent constipation for obvious reasons, it allows the fish to actually make use of the food and a fish that’s hesitant to eat is unlikely to gorge itself and you’ll end up with a lot of leftover food on the bottom of the tank, decaying and affecting water quality.

Vitamin Supplements:

Now, let’s talk about vitamin supplements. These are vital when you want to regenerate a fish, so to speak. The two products I recommend are Vita-Chem and Seachem Nourish, however, I’ve had more success with Vita-Chem. In layman’s terms, Vita-Chem is a multivitamin for fish. That’s as simple as it gets. In more detail though, it’s a vitamin supplement that’s absorbed through the fish’s tissue or ingested directly which means even if the fish isn’t eating, you can add Vita-Chem directly to the water column and still get the benefits. It helps provide essential vitamins like Vitamins C, B1, B2. B6, B12, E, K and numerous amino acids.

This will get essential nutrients to a fish even when they refuse to eat, it’s not a substitute for food, but it might be enough to get the fish to a place where they will eat. Or better yet, it’s very effective in combination with food to strengthen a fish quickly and safely. It promotes a strong immune system, increased growth, fin regeneration, breeding activity and like I mentioned will sometimes restore a fish’s appetite.

When dealing with a sick fish, I add the recommended amount directly to the water column at least twice per week. Sometimes every other day. The days I don’t add it to the water column I add it directly to their food, if they’ll eat.

Seachem Garlic Guard

 Seachem Garlic Guard

Now, another product I always keep handy is Seachem’s Garlic Guard. This is a great flavor enhancer, rich in Vitamin C and is believed to have some anti-parasitic properties to it. I find it much easier than crushing up garlic and mixing it with water. I use this product primarily to defrost frozen fish foods as I find it to be way more beneficial than simply defrosting in dechlorinated tap water. It can also be used to entice a fish into eating and I’ve even heard people say they use it to cure ich. Which I will say is completely false, the antioxidants in Garlic Guard help minimize oxidation caused by parasite’s toxins, but it will not eradicate any parasites by itself. If you want to learn how to actually defeat ich, click here!

If you have any specific questions for me, feel free to message me on Facebook!