For example, there are koi with light blue spots, ones with large red patches on their backs, or all-metallic gold. But the most winning fish often just boil down to these three varieties.

Koi aren't lightweights either; they typically tip the scales around 35 pounds (16 kg), and experts advise filling a pond with about 500 to 1,000 gallons (1,893 to 3,785 liters) of water per each ...