Brown, C., Wolfenden, D., & Sneddon, L. (2018). Goldfish (Carassius auratus). In Companion Animal Care and Welfare (pp. 467–478). John Wiley & Sons, Ltd. https://doi.org/10.1002/9781119333708.ch23

  • Goldfish are generalist omnivores and eat a range of food varieties, from insects to plants. A balanced diet can be provided with some standard commercial flake and pellet foods, with other food types added. As a rule of thumb, goldfish should be fed only as much as they can eat in a few minutes, so that the breakdown of additional food does not cause nitrates, nitrites, and ammonia to build up in the water, which can cause irreversible gill and other damage.
  • Goldfish are motivated to forage amongst substrates and aquatic vegetation. They appear to forage more in sandy substrates than gravel, pebbles, or cobbles,
  • All goldfish need adequate space for shoaling, keeping adequate distances between individuals, maintaining adequate water quality, and allowing all goldfish to reach their full size potential. This requires ponds and aquaria to be many times the expected adult sizes, depending on the number of fish kept together.
  • The volume and frequency of water changes depend on the water quality, and owners should measure water parameters regularly and carefully using standard aquarium test kits (Table 23.1), particularly in small aquaria where the water quality can quickly deteriorate. Any new water should be dechlorinated before being added to the tank because excessive chlorine can be toxic.
  • ammonia: <0.1 ppm; nitrite: <0.1ppm; nitrate: <75 ppm; KH: 70-140 ppm; GH: 150 ppm; temperature: 18-24 C
  • Tank substrates should be provided to meet behavioural needs for manipulation and foraging, such as appropriate freshwater sand. The manipulation of sifting the sand with their mouths may be a behavioural need, which cannot be fulfilled with larger peb-bles or cobbles (Smith and Gray 2011). Substrates and sediments should be kept clean, particularly to remove debris from gravel and to prevent anaerobic fauna development in sand. Sand is a compact substrate but is prone to becoming anaerobic, which can cause problems in aquarium hygiene if not kept clean. Sufficient live aquatic vegetation may be provided, but plant cover should not exceed 50% of the area of the aquarium.
  • In consideration of the relatively complex cognitive abilities goldfish display, their environment should allow for expression of natural behaviour.
  • Owners should also regularly check their goldfish closely for signs of diseases
  • Treatments depend on the disease. Some conditions require a water change or a salt bath (e.g. fungal diseases may respond to salt concentrations of about 2–3 g/L). Others may require commercial disease remedies added to the water, following the manufac-turer’s instructions. More serious diseases, such as internal bacterial infections, require antibiotics. Many treatments have a low safety margin and can be highly stressful to fish if the recommended dosage is exceeded (e.g. formalin and malachite green).
  • Signs of disease include an increased respiratory rate (i.e. faster gill beats per minute) and changes to the fins, skin, eyes, and overall body shape. A change in colour can be indicative of stress or disease; however, goldfish naturally alter in colour over time and may become very pale, even silver, as they reach old age. ‘Dropsy’, in which the body becomes distended with fluid and the scales stick out to give a pine‐cone appearance to the body contour is normally a sign of poor osmotic balance which is commonly caused by bacterial infections.
  • Reduced levels of activity, listlessness, a reduction of feeding behavior, or unusual levels of hiding are all signs that can indicate a problem such as poor water quality. A loss of buoyancy is indicative of swim bladder or diet‐related issues or a variety of causes (Wildgoose 2007). Fish gulping at the surface may be normal feeding behaviour or a sign of poor water quality.