Koi carp have sold for a few million yen each in Japan, where these sacred fish are bred professionally in the manner of thoroughbred racehorses or show dogs.
The supreme grand champion at the annual All Japan Show is the highest honour for a koi breeder.
Here, koi breeding remains an amateur hobby, although the finest specimens are sold for increasingly large amounts, with $5000 considered a top price at auction. Some are rumoured to have fetched more in private sales.
The top sellers are the stud fish, so to speak, and they are especially prolific.
The progeny of two champions will always be more valuable than any others, but with hundreds of thousands of eggs, the challenge is determining which of the small fry are worth keeping.
Only 10 per cent have champion potential, maybe less. The others are sold cheaply to less discerning enthusiasts.
As an investment, their real value is as part of a private home, where a landscaped pond, preferably in the Japanese style, adds value to the property. If that pond contains 10 mature fish with good breeding, you have an important asset.
Koi are divided into 15 varieties for show purposes, just as dogs are divided into breeds. The most valuable are the kohaku, noted for their spectacular red and white markings. Some will grow to 60 centimetres in length, occasionally up to a metre. At seven years, the fish are considered mature 15 to 20 is considered old. A few have reached 50.
The pattern of red and white on the kohaku is the most important characteristic. The white must be porcelain white, not cream, and the red a deep crimson, not orange. The markings, according to Japanese aesthetics, should be clearly defined, as in a painting. Last year's kohaku champion (pictured) is a good example.
Koi are meant to be studied from above their size and shape are other indicators of value. The desired impression is one of power and spiritual strength.
This fascinating hobby can only be enjoyed by Australians in NSW and WA as the keeping of koi is illegal in other states, mainly to prevent the dumping of unwanted fish in rivers or lakes.
From 2009, a licence was required in NSW to sell fish on a commercial basis. Those keeping fish as a hobby are exempt. The commercial licence costs $600 a year and its introduction was a source of angst among professional breeders.
"There are people out there who have four, five, six ponds in their backyards and that's beyond a hobby," Dell Boehner, of Australian Koi Farms at Bringelly, says. This is the most prominent commercial farm in the Sydney area, and well worth a visit.
For those starting out, the most common way to buy stock is at the six auctions held annually by the Koi Society of Australia (KSA) at the Auburn Botanic Gardens. Here, anyone can bid for the koi, which typically sell for $100 for 10 fish about 10 centimetres long. One of these may turn into a $5000 champion, but the chances are remote.
The KSA also holds an annual show, at which fish are judged.
There's enough interest in the Auburn auctions for enthusiasts from Perth to drive across the Nullarbor in search of prime breeding stock. Koi travel quite comfortably in large tanks.
Interest seems to be increasing. More than 100 bidders registered at the most recent KSA auction, including 76 who were not society members. The Asian community, for whom a koi pond is seen as something of a status symbol, is especially interested in this as a hobby.
The investment potential becomes most apparent when noted breeders decide to downsize and sell their stock. This may include hundreds of mature fish fetching a few thousand dollars each - a nice superannuation top-up.
For details of the next koi auction, see ksakoi.com.