Do fish grow to the size of a pond or tank?

The Fish Works

Fish Myth Buster!

Fish have been a much loved common house hold pet for decades. With that title comes a lot of outdated information and myths as to what they need, what they do and how best to care for them. We are here to clear up some of these common misconceptions to ensure happy and healthy fish!

Do fish grow to the size of their tank or pond?

This is one of the most common questions we get all the time in our shop. It is, for the most part, a myth!

It is true that if you place a fish in a small enough environment, it will not reach its full size potential, but this does not mean that the said fish will not outgrow this space.

For example, if you place some koi in a 300L pond, the fish will not grow to their maximum size of around 60cm long. However they will still reach about 35cm, which is too big for this pond. Fish that are too large for their pond will lead to constant issues with water quality that can quickly stress and eventually kill the inhabitants.

Fish have requirements in terms of space given for swimming in order for them to live a happy and healthy life where they will reach their full lifespan without becoming stunted. We recommend that koi need at least 1000L of water to thrive (with a minimum depth of 30cm). Goldfish require at least 100L (with a minimum depth of 20cm).

Can I keep goldfish in a bowl?

Goldfish are often viewed as one of the most common cheap decorative fish. The goldfish bowl is a common image seen in many households, workplaces and media across the world!

Unfortunately however this type of ‘tank’ is unsuitable for our fishy friends. Goldfish produce large amounts of waste, to prevent them from turning their water toxic they require an effective filter to maintain healthy water quality. This small space can also cause them to become stunted and reduce their lifespan.

Goldfish in bowls generally live for a few months at most (occasionally a year or two if given regular water changes). Most people believe this is the average lifespan of these fish however given proper care these species can easily live for up to 20 years!

In order to thrive and reach their full lifespan goldfish require at least 100L of water with a good filtration system. This might look like a medium/large indoor aquarium like the one pictured above. Alternatviely most of the largest, oldest and healthiest goldfish we have seen live in outdoor fish ponds.

If you like the idea of a fish bowl, a nice planted bowl would happily house some freshwater glass shrimp or mussels!

Do fish have a 3 second memory?

The old wivestale that fish have a 3 second memory is one you hear all the time when keeping fish. Those who do own fish will know that this myth is total rubbish!

The latest CSIRO research proves that fish have a far greater cognitive capacity than we has ever thought in the past. Fish are able to recognise faces, each other and even their own reflection. Some goldfish were even taught how to drive cars! (seriously, google it).

Fish and pond owners see just how smart our fish really are during feeding time, when most fish will come swimming excitedly to the edge of the pond/tank. Not only do they have a sense of time, many have been shown to be able to recognise individual human faces!

Fish health is often linked, in people’s minds, to fish happiness. This, in my opinion, is a double-edged sword, for it is not enough to just say “my fish are still alive, so they must be happy”, as we surely wouldn’t say this about any other type of animal. What we can say, though, is that a “happy fish” is far less likely to get sick.

In order to keep our fish happy, we must give them all the things that they need, such as clean water to live in, the right amounts of food (see our full range online) and enough space to swim around freely and lead an interesting life.

The facts

It is our responsibility to provide an environment for our fish, that has enough space and interest within it.

Things such as water plants, a fountain or waterfall, other fish friends and fish of other species all provide a more natural environment for your fish, and in our experience, leads to happier and HEALTHIER fish.

Fish need to be fed in most fish ponds in order to lead a happy and healthy life. It is true that fish will find food naturally within the pond environment, but unless you only have a very small amount of fish in an extremely large fish pond, this amount of food will rarely be enough to provide them with the full range of nutrients that they want (and need). The idea that fish grow to size of their tank is not entirely true, it is important to be aware of what the size of your pond means in terms of fish stock so as to ensure your pond stays healthy and your fish stay happy!