Rare goldfish are sought after by true fish enthusiasts. A rare goldfish is not the same as a fancy goldfish, which is any variety other than the common goldfish. A goldfish becomes rare when it has special qualities that are hard to find in the aquatic world.
Availability to Purchase
The primary reason a goldfish is considered rare is because it's not one you can just go to a pet store and buy. Rare goldfish are usually only kept and bred by experienced breeders or serious aquatic enthusiasts who sell or trade with each other. Most pet stores buy dozens of fish at a time from a breeder who focuses on producing a large quantity of fish rather than individual, quality fish. Generally speaking, if you're looking at a fish from a pet store, there's nothing rare about him.
Some pet stores, especially privately owned ones, will sell rare fancy goldfish. These are usually older fish that have been raised by a dedicated fish keeper before being sold. They're also a lot more expensive than the baby fancy goldfish the store typically sells. A rare fancy goldfish may cost $50, $100, or even more, depending on how special the fish is.
Difficulty to Breed
Some goldfish varieties are just more difficult to breed than others. When breeding is challenging, this makes the fish more difficult to get and therefore more rare. However, a difficult-to-breed fish that's not very appealing won't gain status as a rare fish -- it must also have something about it that makes it desirable to have as a pet. Tosakins are a very rare breed of goldfish that is also difficult to breed. The variety nearly went extinct in the early 20th century because so few of them existed and many were killed in an earthquake in Japan, where the variety was first bred. They are hard to find in Japan and almost unavailable in the U.S., but they are sought after by collectors because of their beautiful, unusual spreading fantail that forms a complete circle when the fish is viewed from above. No other goldfish breed has a tail as impressive as the tosakin, which makes it a rare and desirable fish.
Expression of a Recessive Gene
The distinct characteristics of a rare goldfish are usually expressions of recessive genes -- meaning that these are traits some fish have but most do not. For example, the black, velvety scales of a moor are the expression of recessive genes for pigment and scale texture. The more recessive genes a fish presents, the rarer it becomes. For example, a red and black ranchu with a red body and a black head was judged the most unusual goldfish at the 2000 Goldfish Society of America Convention. Ranchus are considered the rarest and most desired goldfish variety which also makes them the most expensive, so the addition of an atypical coloring set this fish apart among his peers.
In addition to displaying one or more rare genetic traits, a goldfish may be considered rare because she also has perfect body structure for her type. The Goldfish Society of America sets parameters for what makes a perfect goldfish in each variety, such as celestials, orandas, pearlscales and ryukins. These criteria are used when judging fish in competitions. A rare fish like China Gold, a calico ranchu that competed in the Goldfish Society of America Convention in 2000, not only had brilliant calico colors, a red wen (bubbly growth on her head), and no dorsal fin, but also perfect body proportions. She was determined to have no faults in the competition, making her a very rare fish indeed.
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