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How should I keep and care for my goldfish?

05 Oct, 2022

Goldfish (Carassius auratus) are the most popular of all ornamental fish and are known for their attractive bright colours. Goldfish originate from temperate climates and in the wild they live in cool streams, lakes, and ponds throughout Asia and parts of Eastern Europe. Today, there are a wide variety of goldfish available.

Goldfish are social and intelligent animals and are regularly seen interacting with each other and their human caregivers whom they can learn to recognise. Goldfish have a lifespan averaging about 10-15 years, with some varieties living up to 30 years when provided with proper care. Unfortunately, many goldfish do not reach their lifespan potential due to inadequate housing conditions. Housing needs to meet both their behavioural and physiological needs. The following information will help to improve goldfish longevity, health and welfare.

Purchasing a healthy goldfish

When purchasing a goldfish first check that the seller is responsible and that their aquariums are not overcrowded. Healthy fish display clear and bright body colouration and they hold their fins erect. Healthy fish are also alert and swim without undue effort.

Indicators of poor health include fish that sink or bob to the surface; fish that have lumps, bumps, wounds, clamped fins or a trail of excreta and fish that stay in a corner of the aquarium for a prolonged period of time. When choosing goldfish you will also need to consider how large the goldfish will become to ensure that they are provided with adequate space as they grow.

Aquarium size

Minimum tank volume is about 50L and with the following tank dimensions:

Length = 4 x adult body length
Width = 2 x adult body length
Height = 3 x adult body length

Filter capacity has an equally important role to play when setting up.

* Remember that the larger the tank and filter, the better it is for your goldfish.

You will also need to consider how large your fish will be when they reach adult size and the total number of fish you wish to keep. Certain types of goldfish may have increased space requirements, such as slimmer goldfish that are usually more active meaning aquarium size for these varieties needs to be larger and longer than generally recommended for their body size.

Traditional fish bowls are usually too small for goldfish and should be avoided. However, there are some new modern designs that incorporate filtration and lighting which can be good alternatives.

Filtration and aeration

Goldfish are heavy feeders and high waste producers and require efficient filtration of a suitable size to maintain water quality and for aeration. Good filtration will ensure all water is regularly filtered mechanically and biologically via the nitrifying bacteria in the filter media. If the filter does not create bubbles or stir the surface water, an aeration system (such as air stones) can also be attached to ensure that water is well oxygenated. This is important due to the high amount of waste goldfish produce.

When selecting a filter, ensure the current is adjustable. The current should not be too strong if fancy or unusual goldfish types are to be kept as fast currents can make swimming difficult for some of these fish.

Water maintenance

Weekly partial water changes of 10-25% of the tank water are recommended in conjunction with a gravel clean to remove waste and to help keep goldfish healthy.

A siphon may be used – gently shake the siphon briefly in the aquarium to start the flow of water into a bucket below (use a dedicated fish bucket which will not be used for other purposes to avoid any harmful chemical residues). The end of the siphon in the tank can be used to clean the gravel by vacuuming the substrate to remove fish faeces and any uneaten food. Fish can stay in the aquarium while siphoning to minimise stress, though care should be taken not to move too rapidly as this may stress the fish.

After 10-25% of the water is drained, discard and replenish. It is very important to then add water ager (also sometimes called water conditioner) to neutralise chlorine and chloramine and gH & kH generators to the aquarium, in quantities suitable for the new water you will be adding. Then fill the aquarium with cold tap water.

The filter should be rinsed lightly in a bucket of tank water when it starts to get clogged up or on a monthly basis (whichever occurs first). It is important to avoid over-cleaning the filter media as this will remove beneficial bacteria. Without beneficial bacteria in the filter, ammonia from fish waste will not be broken down to less harmful nitrates during the filtering process and this can lead to fish poisoning and death.

The inside of aquariums can be cleaned of any algae build-up by wiping the insides gently with a clean, aquarium safe sponge or with a magnetic glass cleaner. Never use soap or detergents when cleaning an aquarium.

Water quality

Good water quality is essential for any aquarium. Regularly test your water for ammonia, nitrite and nitrate levels to ensure your biological filtration is working, you are maintaining it appropriately and your aquarium is not overstocked or over fed.

Other water parameters to keep an eye on include pH, KH, GH and water temperature.

Correct water parameters

  • Ammonia <0.1ppm
  • Nitrite <0.2ppm
  • Nitrate <50ppm (<110ppm tolerance)
  • pH 6.5-7.5 (tolerance range: 5.0-9.0)
  • KH 70-140ppm
  • GH 150ppm
  • Temperature 20-24°C (tolerance range: 8-30°C)

Plant cover

Goldfish are prey animals and thus require adequate plant cover to prevent stress and facilitate activity. Healthy plant growth is the key to healthy fish as they absorb waste products from the water. Plants also provide environmental enrichment. Plant cover may be provided ideally by real plants and with some imitation plants if needed. Please ensure all plants are safe for fish. Driftwood and decorations may also provide cover.

The more cover provided, the more active your goldfish will become. Approximately 50% cover is recommended. Ensure that any decor is free from sharp or rough edges that may injure your fish or any small holes in which they may become trapped as they grow larger. This is especially relevant for some of the unusual varieties which are generally not strong swimmers and fancy goldfish which may have impaired vision.

To prevent algae outbreaks, aquariums should ideally be kept away from direct sunlight or windows. Aquarium lights may be left on for 8 hours a day.

For more information, we recommend that you talk to an experienced aquarist or fish vet. Goldfish with unusual body types may require specialised care and additional research is recommended for these varieties.

Article supplied by RSPCA

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