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.