Goldfish Guide

Keeping a goldfish appears simple and straightforward, but the typical goldfish bowl is not a suitable living space for these small and attractive animals. Find out here what you should consider when keeping goldfish and what care these silent companions need.

What are the distinguishing features of a goldfish?

Goldfish belong to the carp family and were kept as ornamental fish from early on. Over the centuries, numerous manifestations of the goldfish have appeared during breeding. Hence, the name “goldfish” is quite misleading nowadays, because there aren't just golden breeds, but a wide variety of colour combinations. There are several forms in the terms of the shape of the fins and tail too. Find out more in the following paragraph.

What goldfish breeds are there?

All well-known goldfish belong to the same domestic species. Since this is considered a highly robust and easy-to-keep type of fish, breeders have dedicated themselves to keeping these attractive animals in ponds from an early stage. They were bred in China over 1,000 years ago and are the second-oldest type of decorative fish in the world after the Koi.

Hence, it's hardly surprising that nowadays there are a large number of different goldfish breed varieties. In China alone, there are more than 350 to 400 known types of fish.

Breeding of veiltail goldfish began in the countries of origin China and Japan, where these fish have take on cultural significance as a symbol of happiness and fertility. Along with numerous veil and body shapes, different colours and patterns are also found.

However, you should ensure that some of these breeds are banned on animal welfare grounds. One can even talk of “torture breeding” when it comes to some of the drastic changes to the skeleton, head area and missing veils. Thus, before purchasing you should inform yourself about the different shapes and only purchase permitted goldfish.

Where do goldfish originally come from?

Goldfish are freshwater fish that originally came from eastern Asia. As mentioned, they were  bred as pets as early as 1,000 years ago to primarily serve a decorative purpose. As a result, it isn't easy to pinpoint their exact origin.

Whilst the crucian carp was considered the progenitor earlier on, this has now been dispelled by classic morphometric comparisons. Comparative studies on the genomes of goldfish and carps are yet to confirm whether the prevalent perception that goldfish came from the common Prussian carp is correct.

Since it is scientifically not customary to identify the species of pets, the oft-used species name Carassius auratus is actually not entirely correct. The name Carassius gibelio forma auratus (Bloch, 1782) would be scientifically correct, though the first name is primarily used in trade.

What should I bear in mind for keeping a goldfish?

First of all, a sufficiently sized aquarium is required for keeping a goldfish. Housing them in small round vessels, as was common decades ago, is not species-appropriate at all and generally leads to the animals passing away quickly. After all, fish have a huge urge for movement, and both the water quality and oxygen level of such small vessels leaves much to be desired.

Depending on the variety, goldfish can become up to 35 or 40cm in length. However, many of the forms intended for aquariums only reach around 20 to 25cm. Nevertheless, this means that goldfish owners need to purchase a sufficiently sized aquarium. As a rule of thumb, a goldfish needs an aquarium with at least 55 litres of volumetric capacity. You should add a further 38 litres for each additional fish.

However, some types are so big that they are only suitable for ponds. In order for them to be able to hibernate there, the pond must be at least 1.5m deep. If the pond is shallower, goldfish must be kept in a cold-water aquarium during the cooler months, which is not simple. Hence, get yourself well informed on the needs of individual varieties.

In general, goldfish are undemanding for their owners. The water does not need heating, and it is sufficient when it is warmed up passively from around 12 to 23°C through the temperature of the air in the room

A filter is important to guarantee good water quality. It should be adapted to the size of the aquarium and feature three stages: the mechanical stage eliminates coarse particles like droppings or excess food, whilst the chemical stage does away with odours, discolourations and other organic substances. The biological stage breaks down excrement and ammonia with the help of bacteria.

Plants in an aquarium are not absolutely necessary for goldfish, especially because they normally just eat them. Artificial plants and pieces of wood can thus also be used as decoration. It's important that the objects have no sharp edges that could injure the fish. Don't put too much decoration in the aquarium in order to leave the fish enough room for movement. Hence, plants are best off being placed on the edges. Shingle can also be used on the aquarium floor. When equipping the aquarium and adding new plants or objects, suitable disinfection procedures should always be carried out.

Before fish are placed in aquarium and whilst they are kept there, the quality of the water should always be thoroughly inspected. High levels of chlorine, ammonia or nitrate can damage or even kill fish. Fluidity tests are a more suitable form of inspection than test strips, which are often difficult to interpret.

What type of diet do goldfish need?

The right food is an important prerequisite for a healthy goldfish. Since they don't have any sense of satiety, it's important to provide a suitable quantity of food. As a general rule, only give enough food for them to eat in a minute.

Overfeeding low-quality food can lead to obesity and ultimately to severe liver damage. Instead of offering a large quantity of food once a day, it's better to give several smaller portions each day.

Like all animals, goldfish like variety, though a high-quality main food is more important. Commercially available fish food in the form of dried flakes or pellets can occasionally be mixed with live food like frozen mosquito larvae. They also like eating lettuce and Chinese cabbage. Plants in the aquarium are also a source of nutrition for goldfish, which can lead to the contents of the tank soon being completely eaten up. Robust growths like tape grass that cannot or can hardly be eaten are good additions to the plants that goldfish love.

Floating food should be soaked for a few seconds beforehand so that it sinks and the goldfish take in less oxygen whilst eating. The same applies for freeze-dried food. Soak it in a cup with water from the aquarium so that it doesn't expand in the goldfish's stomach and thereby cause problems for it swimming.

How long do goldfish live and from which illnesses can they suffer?

If kept in optimal conditions, these ornamental fish can live to be over 20 years old, therefore make companions for the home for many years. However, the requirements are a suitable aquarium and regular maintenance, as only in this way will illnesses such as fungi be avoided.

The immune system of goldfish is highly effective. Nevertheless, these animals can reach their limits due to unfavourable circumstances and fall ill. In over 50% of such cases, no help is possible. Prevention through correct housing and care is thus the basic requirement for these aquarium inhabitants to live a long and healthy life.

These tips help to prevent illnesses:

The initial installation of an aquarium is particularly critical, because the new ecosystem must first be consolidated. As a result, goldfish should not be placed in newly set-up tanks too soon.

Goldfish can of course already be sick when purchased, therefore you should only purchase fish that appear healthy. If newcomers are added to an existing community of fish, they should initially be placed in quarantine for at least four weeks. If no signs of illness have cropped up in this time, they can join the old stock. At first you should just exchange some water between the two tanks in order to get the different animals' immune systems used to each other.

Since plants can also pass on illnesses, new ones should always be disinfected with a potassium permanganate solution before being added to the aquarium.

These preventive measures are therefore also important for goldfish lovers, since there are very few vets who know how to treat sick ornamental fish. Additionally, only few illnesses can even be treated with medication. Before medication is prescribed, a precise diagnosis is important in order not to harm the animal further. Don't therefore consult your dog's vet, but an (ornamental) fish specialist.

Where can goldfish be purchased?

Goldfish and all derived varieties are the most popular and purchased pets worldwide. Nowadays, the fish consequently don't just come from classic fish breeding countries in South and East Asia, but from large breeding centres in Italy, Florida and Israel too. Goldfish offered by all fish-keepers are therefore mainly imported, so you should pay attention to a few important points for making a purchase.

At first, you should consider the recommendation outlined in point 3 and only purchase from breeds permitted in Germany in order to avoid animal cruelty and apparent “torture breeding”.

For the health of the fish, you should also carefully inspect the conditions in which they are kept, i.e. the tank in the store. Only buy fish from healthy tanks in order to not bring diseases into your aquarium. Retailers' tanks are generally overfilled, but the fish should appear healthy nonetheless. In order to check this, you should visit the fish trader several times and only buy fish that swim around cheerfully, have an appetite, stretch out all their fins and are in good health, evident by the surface of their skin. If the fish appears apathetic, has dull eyes or fins that it clamps, you should steer well clear!