It seems a Ghostie is a mis-fit or the right-fit Koi, it just depends who you ask.
So, what are these Ghost Koi I've been hearing more and more about? Well, it seems they have been around since the early 1980s when a British farmer allowed a mirror carp to spawn with a Koi. The offspring from a cross of a metallic Koi and a wild, dark-colored carp are known as Ghost Koi. Notably, the most striking areas of a Ghost Koi are the metallic head and flashy pectoral fins that glimmer in the sunlight and disappear into the depths of a dark pond like a ghost, hence the name. They are considered a hybrid, being a cross within varieties of the species Cyprinus carpio creating feritle offspring.
Koi purists tend to relate to them as mis-fits that should have been culled and do not find value in them. Garden pond owners relate to them as being vigorous, hardy, tame, rewarding to view, and more affordable. A novice or beginning Koi enthusiest may find them a great first Koi as they are considered tough as nails requiring less pampering, have a natural high disease resistance, and grow rapidly, because of the stronger genes passed from the broadstock carp. As they are not a high-grade Koi, requiring generations of breeding and farming, a larger percent of offspring reach the market making them more affordable. The coloration is made up of whites, silvers, charcoals, gun-metals, and golds. Ghost Koi can also have a variation of scale patterns, including fully-scaled small scales, large mirror scales, linear (lateral line and dorsal) scales, and leather (scaleless) variations. Gin rin (sparkling) variations can also occur within the fully scaled.
Because of their resilience, they require less demanding and sophisticated filtration systems to maintain superb water quality and do well in garden ponds; this also makes them more affordable. They are less effected by common Koi ailments, such as ulcers, which is another advantage for the novice and hobbist. They do benefit from a large pond and a well-balanced food compared to premium-grade food and color enhanced food. Their color pattern appears on younger Koi and is stable throughout its life.
So, it seems, beauty is in the eye of the beholder and Ghost Koi are finding their niche in the market and in ponds.