Understanding medaka gender identification is essential for successful breeding and tank harmony. This section introduces basic visual traits.

Male: Notched dorsal fin, parallelogram-shaped fins.

Photo: Takayasu Oba

Female: Smooth dorsal fin, trapezoidal fins.

Photo: Takayasu Oba

Some strains are more difficult when it comes to medaka gender identification, especially those with modified fins and shapes.

Yes. Among improved medaka breeds, altered body shapes and fin extensions make it more challenging. Still, the spine and dorsal fins remain key indicators.

Hikari Body Type

Male: Fins are parallelogram-shaped.

Photo: Takayasu Oba

Female: Fins resemble trapezoids.

Photo: Takayasu Oba

Daruma Body Type

Male: Short body, notched dorsal fin, wide fins.

Photo: Takayasu Oba

Female: Smaller fins, smooth dorsal.

Photo: Takayasu Oba

Fin Long Breeds

Fin-Length Male: Jagged fin tips.

Photo: Takayasu Oba

Fin-Length Female: Rounded tips.

Photo: Takayasu Oba

Swallow

Swallow Male: Judge using non-extended portions.

Photo: Takayasu Oba

Swallow Female: Easily distinguishable.

Photo: Takayasu Oba

Longfin

Longfin Male: Elongated dorsal and spur fins.

Photo: Takayasu Oba

Longfin Female: Similar to normal body females.

Photo: Takayasu Oba

Real Longfin

Real Longfin Male: Slit in dorsal fin, jagged tips.

Photo: Takayasu Oba

Real Longfin Female: Identify when young.

Photo: Takayasu Oba

Wide-fin

Wide-fin Male: Broad fins, altered dorsal.

Photo: Takayasu Oba

Wide-fin Female: Rounded, wider fins.

Photo: Takayasu Oba

To wrap up, here’s a quick review of medaka gender identification across types covered.

Once you learn to identify normal body type medaka, the rest becomes pattern recognition. If you're unsure whether you have a male or female, return to these fin and dorsal indicators.

🔗 Further Reference: Aqua Life Japan Blog

🌐 External Reference: Japanese Rice Fish on Wikipedia

📘 Learn More: Medaka Egg Hatching Time | Lifespan of Medaka | Browse Live Medaka | Back to Top