Nishiki Black & Yellow Medaka (Oryzias latipes) is a striking ornamental variety of Japanese rice fish prized for its bold contrast and ease of care. 

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Appearance

• Coloration: Deep black body with bright yellow/gold patches or overlay
• Pattern: Can vary—some show mottled “koi-like” patterns; others have cleaner contrast
• Size: ~3–4 cm (1.2–1.6 inches) adult length
• Body type: Slender, torpedo-shaped with subtle metallic sheen

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Origin & Background

• Derived from selectively bred Japanese medaka strains
• “Nishiki” generally refers to multicolored or ornamental lines, similar in naming style to koi varieties
• Species: Oryzias latipes (native to Japan, Korea, and China)

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Care Requirements

Tank / Container

• Minimum: 5 gallons (larger groups preferred)
• Can also thrive in:
  • Outdoor tubs
  • Patio ponds
• Gentle filtration recommended, but not mandatory in planted setups

Water Parameters

• Temperature: 10–28°C (50–82°F) — very hardy
• pH: 6.5–8.0
• Hardness: Adaptable (soft to moderately hard)

Lighting

• Bright lighting enhances yellow coloration
• Sunlight (for outdoor setups) brings out best contrast

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Diet

• Omnivorous and easy to feed:
  • High-quality micro pellets or flakes
  • Live/frozen foods (brine shrimp, daphnia, mosquito larvae)
• Color-enhancing foods will intensify yellow tones

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Behavior & Compatibility

• Peaceful and social schooling fish
• Best kept in groups (5–10+)
• Compatible with:
  • Other medaka varieties
  • Small peaceful species
• Avoid keeping with aggressive or fin-nipping fish

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Breeding

• Extremely easy to breed:
  • Females carry eggs attached near the vent briefly before depositing
  • Spawning occurs almost daily in warm conditions
• Provide:
  • Floating plants or spawning mops
• Eggs hatch in ~7–14 days depending on temperature

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Why They’re Popular

• Hardy (great for beginners and outdoor setups)
• Unique black & yellow contrast uncommon in many small fish
• Active and visible swimmers
• Breed readily, making them ideal for hobbyists and breeders

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Tips for Best Color

• Keep in dark substrate tanks or tubs
• Provide natural sunlight when possible
• Feed varied, high-quality diet
• Avoid mixing with too many other strains if you want to preserve coloration