Fish, Tanks and Ponds

Fish, Tanks and Ponds
A comprehensive guide to fish

Carassius auratus auratus


Photos by Andy Rapson


Carassius: Latinization of , karass, karausche, European crucian carp.
auratus: meaning gilded

General Notes:

Most people will have won a goldfish at the fair at some point in their life. It is one way that a lot of people find their way in to fish keeping. Sadly the fairground goldfish often kept in a bowl don't thrive and die a premature death. Goldfish grow quite large, adults can reach 30cm quite easily and so a goldfish bowl isn't suitable as a home and should be consigned to history. Ideally a suitably sized outdoor pond with an area at least 1m deep for over wintering. Standard  goldfish are extremely adaptable, very hardy and if cared for properly they will live for decades and will continue to grow all through their lives unlike their line bred relatives the fancy goldfish which need very different care.

Food and feeding

All goldfish are omnivores with a strong leaning to vegetable matter. Adult goldfish need a diet high in fibre and low in protein, young fish which are growing quickly need a diet high in both fibre and protein.

In  an experiment goldfish fry were split in to three groups and fed on three different diets, one group were fed on live baby brine shrimps, group two were fed 50% brine shrimps and 50% dried food and group three were fed dried food. After three weeks the first group had the best growth, group two with the mixed diet came second and the group fed on dried food had poor growth. However this changed after just three weeks when group two with the mixed diet grew fastest.

Ideal foods for goldfish are: duckweed, cucumber slices, skinless processed peas, algae, blanched spinach, occasional live or frozen daphnia, bloodworms and similar. Along with algae wafers and flake food which has been wet immediately prior to use so that it sinks.


When in breeding condition male goldfish like many of their relatives will develop tubercles which show as small white dots on their gill covers and surrounding area these are absent from the female.

All goldfish despite their appearance are the same species. This means that all the different varieties are able to breed successfully with each other. In a mixed variety aquarium this might lead to undesirable offspring which have no commercial value and which you may end up stuck with.

Healthy well cared for goldfish will come in to breeding condition on a regular basis without any special spawning triggers.  All goldfish are egg scatterers, the male usually drives the female and as she is being chased the eggs and sperm are released. The eggs are semi adhesive and will stick to plants. The adults are avid egg eaters so if you want to grow some fry you will have to quickly remove the parents after spawning.

Goldfish myths

  1. Goldfish will only grow to the size their tank allows. - False
    Poor care stunts goldfish not tank size.
  2. If a goldfish is stunted due to its tank its internal organs will keep growing. - False
    Don't know who thought of that one but whoever it was doesn't know much about fish.
  3. goldfish need a high protein diet. - Only partly true.
    Only very young and rapidly growing fry need lots of protein.
  4. Goldfish only need a bowl and water to live happily. False.
    Goldfish are very hardy and adaptable which means they can survive for a time in poor conditions. They will die prematurely in such conditions and most definitely won't live happily in them.
  5. goldfish only live for a few years. - False
    goldfish are capable of living for many years with good care.

Information at a glance

pH: 7 - 8
dGH: 4 - 15
Temperature: 4 - 25°C (39 - 77°F)
Diet: Herbivore / Omnivore
Size:30cm (12in)+
Min tank size: 225 litres
Difficulty level: Intermediate
Aquarium type: Species
Swimming level: All levels

Distribution and habitat

distribution map for  Goldfish

Origin: China and Japan, but has been introduced throughout the world.

Habitat: Slow moving or still water in canals, lakes, ponds, ditches and rivers. Capable of adapting to most conditions


Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cypriniformes
Family: Cyprinidae
Genus: Carassius
Species: C. auratus auratus, (Linnaeus, 1758)

Common name:

Synonyms: Cyprinus thoracatus, Cyprinus mauritianus, Cyprinus maillardi, Cyprinus langsdorfii,
Cyprinus gibelioides, Cyprinus auratus, Carassius pekinensis, Carassius discolor, Carassius coeruleus, Carassius chinensis, Carassius carassius auratus, Carassius auratus wui, Carassius auratus cantonensis, Carassius auratus