A new variety of koi appeared in the trade in the early 1980′s under the intriguing name of ghost koi (or ghost carp). Nearly two decades later, the range of fish available to the trade under this description is almost as diverse as the number of outlets that sell them.
The popularity of the ghost koi (or ghost carp) in the UK is so great that in a recent survey, pondkeepers voted ghost koi as the nation’s favourite koi variety, surprisingly head and shoulders above any of the more conventional and more colourful koi varieties.
Indeed, the ghost carp is not recognised by koi enthusiasts as a koi variety and would certainly not be found in the pond of a koi purest. No wonder therefore that the unprecedented rise of the ghost’s popularity has not been widely or ‘officially’ acknowledged over the past few years and that its poor coverage in pond and koi publications does not correspond to its popularity in the UK.
What are ghost koi / ghost carp and what makes the nation’s favourite koi variety so popular?
It is not simply the ornamental trade that is so obsessed with this variety. Over the last decade, ghost carp (notice the subtle change in the name) or ‘ghosties’ have also shot to the top of the list of most carp anglers. Having stalked common and mirror carp in lakes for many years, the introduction of ghosties into the same waters has added a new flavour to the angler’s catch, adding another variety and an unusual splash of colour to the angler’s catch.
Ghost koi and ghost carp are the same fish and are carp hybrids, the result of a cross between a metallic koi and a common carp. NB This is not a hybridisation between species but between varieties of the same species producing fertile offspring.
Recognising that koi are the same species as carp (Cyprinus carpio) and it is through man’s selective breeding that koi occur in an infinite array of colours and patterns, it is not surprising that a cross between metallic koi and common carp produces viable offspring – ghost koi. These offspring exhibit ‘hybrid vigour’ where the hybrids outperform the parents’ growth, fertility and health.
Ghost koi are made up of variations in: Colour (Gold, Silver etc)
Intensity of metallic lustre
Scalation (Pattern and type of scales)
These are controlled and determined by the characteristics of the broodfish
The conventional cross to produce ghost koi will be:
Purachina (platinum ogon) White ghost koi
or Yamabuki (yellow ogon) x carp = or Gold ghost koi
However, the production of ghosts is not limited to a single cross of metallic koi x carp. Variations are possible between the 4 scale types in carp:
Common (Fully scaled fish – small scales)
Mirror (Fully scaled fish – large mirror scales) ‘Doitsu’
Linear (Partially scaled mirror with line of scales along lateral line and dorsal) ‘Doitsu’
Leather (Scale-less fish of mirror variety)
Depending on specific crosses used, these crosses generally produce offspring offering an array of the above 4 scale patterns. There are also specific crosses between Linear and Leather carp, 25% of which will not develop into viable fry, possessing a lethal gene. Gin Rin variations (sparkling scale) can also occur in the fully scaled (common) ghosts.
Some work over recent years at Brooksby College has also shown that ghosts can be produced by crossing ghost x ghost, producing 2nd generation ghosts. However, the offspring of this cross are less metallic than the original koi x carp hybrids and the wild-type fish (throwbacks) are more numerous than the original metallic koi x carp cross.
This range of crosses may explain to some extent the diverse range of ghosts on the market, from the duller ‘charcoal’ ghosts through to ‘gun-metal’ and the very conspicuous ‘titanium’ ghosts.
A higher grade ghost is also available on the market which in fact is not produced in the above manner. For example, when an all metallic koi cross is carried out, and with koi not breeding true, then ‘throwbacks’ occur where individuals are produced that exhibit some of the ancestral ‘wild-type’ characteristics. I.e. some progeny exhibit the darker carp characteristic that has diluted some of the pure metallic features of the broodstock. I.e. they are not pure metallic. If this occurs in the more complex coloured koi varieties e.g. kohaku, sanke, showa etc then the throwbacks are culled as having undesirable and unmarketable characteristics. However, the throwbacks from metallic crosses resemble excellent ghosts, are generally more metallic than a standard ghost and are therefore marketable as a ghost koi.
It is therefore possible to see why there is such a range of ghost koi varieties on the market. They can only loosely be defined as a colourless, dark metallic fish of koi shape with incomplete metallic skin, head or scalation.
Ghosts do not only share their shape and colouration with koi but also the way in which colours can develop over time and with the age of the fish. At Brooksby, where each year significant quantities of ghost koi are produced on the college fish farm, some recent work has shown that ‘disappointing’ 1 year fish can improve into their second year. Where relatively drab fish had been harvested in year 1, if left for another year to grow on, ghost-like characteristics had really improved, developing into a stunning fish. Pectorals had become completely metallic, flashing in the sunlight and heads had become significantly more metallic and noticeable.
Why are ghost koi so popular?
Ghost koi offer excellent value for money. For a number of reasons they are cheaper than standard koi but this does not really make them a second-rate alternative to koi.
Ghosts are cheap to buy because compared with koi and other selected ornamental pondfish they are relatively cheap to produce. Although they are farmed in an identical way to koi, they offer a number of attractive benefits to the ghost koi farmer.
Koi breeders and farmers have traditionally passed experience and expertise down through generations to develop high quality and reliable bloodlines. When they breed from these bloodlines, only a minute fraction of the spawn reaches the market as high quality stock, commanding a high price.
By contrast, broodstock required to produce ghosts are readily available at a reasonable price without the necessary investment of time and effort over many generations. In addition, the majority of ghost offspring are marketable, and the expertise, time and expense of culling is not required on the same scale as in koi production and as more fish reach market per spawn, the unit price of each fish is greatly reduced. However, the research, experience and knowledge of which particular broodstock produce the best ghosts is essential to provide the market consistently with top quality metallic ghost koi.
As ghosts are hybrids of koi and carp, they are more vigorous than koi producing better growth and offering better disease resistance. In koi breeding, through years of selection for colour and shape, inbreeding of stock has reduced koi vigour rendering them weaker, slower growing and more susceptible to disease than their wild ‘carp’ ancestors. This benefits both the ghost koi farmer and keeper who experience accelerated growth and enhanced health, vigour and vitality over their ‘true’ koi cousins by virtue of the stronger genes passed on from the carp broodstock.
Having had experience of farming and keeping both koi and ghosts, the contrast between the husbandry of both varieties is quite stark.
Koi generally have to be treated/medicated almost as a matter of course and great attention shown to water quality and nutrition to keep them in top condition and to achieve breeding success. Having more recently had experience at farming ghost koi no medication whatsoever has been required to treat ghosts at Brooksby College fish farm and growth has exceeded that experienced in koi farming. A testament to the ghosts vigour, disease resistance and undemanding physiology compared with that of koi.
The spin-off for the ghost koi keeper is that they can taste koi keeping but without the disease hazards feared and often experienced by conventional koi keepers. As their investment in ghost koi is likely to be less than in koi then if they lose a fish they are less likely to suffer a significant financial loss and as their requirements are less demanding, they can be kept quite satisfactorily in a garden pond environment. In fact it has been argued that ghost koi are even hardier and less demanding than goldfish.
Money can also be saved by not having to go to the expense of extensive filtration systems that many koi keepers need to install to maintain a stable and suitable water quality for their relatively frail koi.
Where ghosts are kept with koi, they often outgrow their weaker relatives, courtesy of their stronger genetic make-up. This phenomenon can also be seen in many ponds where drabber koi or goldfish outgrow and are healthier than the more visually striking and purer varieties. I.e. they retain some of the vigorous wild-type genes.
The record carp in the UK is over 55lbs. Ghosts have reached 30lb in the UK (so far) and there is no reason if given the time and space, why they should not get that large in similar conditions. They certainly have the ability to outgrow koi.
Ghosts can also become exceptionally tame, coming to eat from your hand. This ‘friendly’ nature is often their most appealing feature as they rush toward prospective purchasers in retail stock tanks asking to be taken home and put in your pond.
Consequently ghosts can be very rewarding pond fish. They are undemanding in terms of their husbandry but will benefit from a large pond. While maintaining some ornamental value, they do not suffer the shortcomings and limitations of other ornamental varieties and often endear themselves to pondkeepers as a very rewarding fish for their confident character and exceptional value and growth. No wonder they are the UK’s favourite koi variety.
Care Tips …. There are very few care tips and nothing specific to the ghost koi.
Keep them in as large a pond as possible and treat them as a pond fish rather than a koi. They do not require a premium koi diet with colour enhancers but a well balanced pond fish diet will be sufficient for this undemanding fish. They can be fed earlier in the Spring and later in the Autumn than koi without risking associated health problems experienced in purer inbred ornamental varieties.
As ghosts will readily consume quantities of food, the pond must have effective means of removing solids to maintain clarity coupled with effective biofiltration to breakdown toxic metabolic by-products. I.e. normal pondfish practise.
Selection tips
Be careful when selecting ghosts for your pond to take into account the sizes and natures of your existing pond fish. These vigorous and competitive fish can change a well balanced ‘placid’ pond into an aggressive free-for-all at feeding time. Try to buy them smaller than your existing fish. They will soon outgrow the other inhabitants anyway, but it allows your existing stock to adjust to the new ghost carp and will save you money by buying small ghosts to start with.
Personal taste dictates which ghosts you select, but shop around as a whole range of colour variants in ghosts exists. Huge quantities are consistently imported from Israel and a lot of UK bred ghosts are also on the market offering an acclimatised and short-travelled fish. Something to consider when buying.
Commonest Ailments
It is very rare to find ghost koi with ulcers or other common koi ailments. In fact this is an opportunity to buy a ‘koi’ without the health and disease risks associated with koi.
However, non life-threatening carp pox can be quite common is Spring but will fade with time and as temperature rises.
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