Medaka appraisal guide

Even among the same varieties—"Yōkihi" or "Kaminoyu"—evaluation varies greatly depending on body color depth, luster and body light quality, system stability, and body shape quality. Medaka that appear identical at first glance produce price differences through the complex interplay of these elements.

What determines the price

Body color depth and uniformity
High
The deeper and more uniformly colored the body across its entirety, the higher the evaluation. Each variety has a desirable body color, and container color and lighting conditions affect color appearance.
Luster and body light density and range
High
For luster-type medaka, luster density and distribution range; for Kaminoyu-type, the range covered by body light (full-body, etc.) is the core of evaluation. Specimens with higher density rather than sparse distribution are evaluated more highly.
Body shape and spine alignment
Medium
Individuals with straight spines and well-balanced body proportions are rated highly. Curvature and deformities may be hereditary, so caution is necessary.
Strain Stability
Medium
Lineages in which traits are expressed consistently across generations have higher reliability. Even among offspring from the same parent fish, differences in lineage management have a significant impact on traits.
Health Status and Swimming Posture
Medium
Select individuals that swim actively in the water with dorsal fins held upright and exhibit vigor. Unstable swimming patterns or a tendency to sink are signs of health problems.

Appraisal points

Confirm Body Color in an Appropriate Environment

Good:: Under black containers and stable lighting, uniform coloration is observed across the entire body, and color is consistent.
Caution:: In white or transparent containers, color may appear pale due to protective coloration. Observation in a black container is recommended before purchase.

Confirm Swimming Behavior and Posture

Good:: The fish swims actively in the water column with dorsal fin erected and maintains stable swimming.
Caution:: Floating at the water surface, remaining still at the bottom, or swimming at an angle are signs of poor health.

Confirm Body Shape and Physical Appearance

Good:: Spine is straight and body proportions are balanced overall. Fins are intact and undamaged.
Caution:: Spinal curvature, fin loss, and deformities may be hereditary, so caution is necessary when considering use for breeding.