While everyone thinks and talks about finding that overlooked 'diamond in the rough' tosai in a domestic breeder's tank, buying the tosai is only the beginning of a GC's journey.
If its new owner places it into an aquarium, forget about it.
If its new owner places it into a water garden, forget about it.
If its new owner places it into too small a koi pond, forget about it.
If its new owner places it into too shallow a koi pond, forget about it.
If its new owner places it into an overstocked koi pond, forget about it.
If its new owner places it into a koi pond with insufficient circulation, forget about it.
If its new owner places it into a koi pond with insufficient turnover, forget about it.
If its new owner places it into a koi pond with insufficient aeration, forget about it.
If its new owner places it into a koi pond with insufficient filtration, forget about it.
If its new owner fails to properly maintain the pond, forget about it.
If its new owner changes too much or too little water, forget about it.
If its new owner changes water too frequently or too infrequently, forget about it.
If its new owner feeds too much, too little or the wrong kinds of food, forget about it.
If its new owner doesn't stay on top of testing the water, forget about it.
If its new owner improperly adds various chemicals and medications to the pond, forget about it.
If its new owner doesn't know how to spot, identify & treat parasites and pathogenic bateria, forget about it.
If its new owner doesn't protect the koi from predators, forget about it.
If its new owner doesn't show the koi, forget about it.
If its new owner doesn't know how to condition the koi for showing, forget about it.
Come to think about it, breeding & buying that domestic GC tosai is the
easy part!