Scale arrangement and reflection are useful clues when identifying koi. They also deserve careful observation as part of the fish's surface condition, without treating scales as armor that makes poor water harmless.
Scales, Skin, and Mucus
Scales form part of the fish's body covering, with skin and mucus also important to surface protection. Damage can affect more than a visible scale. Avoid rubbing, polishing, or scraping the surface, and minimize unnecessary handling when viewing ordinary features.
Fully Scaled and Doitsu Fish
Fully scaled koi have a regular covering of scales. Doitsu forms have reduced scaling, sometimes with conspicuous rows of larger scales. A naturally sparse scale arrangement is not automatically evidence of injury or disease. Compare the fish's known baseline before interpreting an apparent gap.
What Ginrin Describes
Ginrin refers to reflective scales that sparkle as the angle changes. Metallic skin is a separate characteristic. A fish can have Ginrin scales without belonging to a metallic variety, so look at the head and skin as well as the scale flashes when identifying it.
Pattern Is More Than Scales
Color and pattern are not simply a collection of painted scales. Gosanke is the group of Kohaku, Sanke, and Showa; it does not mean that every member has three colors. Kohaku are red and white. Names for sheen, scaling, and color arrangement describe different aspects of the fish.
Notice New Surface Problems
Missing scales after an injury, raised scales, redness, open sores, or abnormal mucus should be recorded and assessed. Check water and equipment and seek appropriate fish-health help for persistent or serious signs. Do not choose a medication from a photograph alone. Use fin anatomy, color-change checks, and variety vocabulary to describe the fish accurately.