The Common Goldfish must the most commonly-kept fish in the world, althoug its popularity as an aquarium fish has diminished against the hugely popular tropical fishes which are now available, both for freshwater and marine aquariums. Having said that, the Goldfish can still be as source of enjoyment as long a it is treated respectfully, and given a large enough aquarium.
There are several extensions to the Goldfish theme for, although only consisting of one variety, Carassius auratus, many years of aquarium breeding have produced several different strains. The London and Bristol Snubunkins are the two most basic ‘improvements’. The London has a shorter tail against the Bristol’s well-developed broad-lobed tail but it is in the color development where the attraction lies. Pigmentation under the skin produces violets, blues and reds which, coupled with the non-reflectivity of the scales produce a wide range of colorations quite distinct from the single red/orange color of the metallic-scaled Common Goldfish.
The Comet, another metallic fish, has a large forked tail almost as long as the body. This specie can swim at high speed but only for short periods.
All of the varieties are suitable for both aquarium and pond culture. They are known as ‘singletails’ as the tail fin comprises a single unit. The following varieties have double tails and are known as ‘twin-tails’.
From here on, the traditional Goldfish body shape has undergone further development and has become more and more egg-shaped. By further selective breeding, more flowing fins have been added, in some cases the dorsal fin lost, eyes have become telescopic and tails flattened and curved almost horizontally.
These varieties form the bulk of the Fancy Goldfish interest and include all the colorations and scale patterns. There is even a jet black Goldfish called the Moor.
Typical Fancy varieties are Fantail, Veiltail, Jikin, Ranchu, Ryukin, Wakin, Oranda, Lionhead, Celestial, Bubble-eye and Tosakin and each variety has its own characteristic qualities.
Most of these varieties are not suitable for pond culture and will have lost much of their swimming prowess. Their internal organs will have become cramped through the shaping of the body with the result that some will develop swimming or balance abnormalities.
Other coldwater fishes
Whilst there are many other species of coldwater fish suitable for aquarium culture, recent legislation has made the importing, selling and keeping of such fishes much more difficult, especially those fishes imported from other countries. The reason for this is quite simple: because the fish share the same water conditions in their country that exists here, any imported fish that is set free into our native waters could seriously affect our own native fish stocks, either by predating on them or by breeding at such a fast rate that they are outcompeted for natural food.
At the time of writing, licences are required to be held by both the vendor and purchaser in respect of non-native fishes. Those fishes most affected are many found naturally in North American waters; these include Pimephales, Cyprinella, Lepomis, Notropis, and Umbra, all very attractive aquarium subjects.