Black Ricefish (Oryzias nigrimas)

⚫ Black Medaka Ricefish (Oryzias latipes) Care Guide

Also known as the Japanese Ricefish, Black Medaka, or Japanese Killifish

The Black Medaka Ricefish is a selectively bred color form of the Japanese Ricefish, featuring a deep jet-black body with subtle metallic highlights. Hardy, peaceful, and highly adaptable, this species is ideal for planted aquariums, nano tanks, and outdoor tubs.

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Tank Requirements

Minimum Tank Size: 30 litres

Temperature: 16–26°C

pH: 6.5–8.5

GH: 6–18

KH: 4–12

TDS: 150–350 ppm

They thrive in stable water with gentle filtration and are suitable for both heated and unheated aquariums. Clean, well-oxygenated water supports long-term health.

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Habitat Setup

Recreate their natural, slow-moving environment with:

• Fine gravel or sand substrate

• Dense live plants and floating plants

• Open surface swimming space

• Gentle to minimal water flow

Floating plants such as Frogbit, Salvinia, or Water Lettuce help diffuse light and encourage natural behavior and spawning.

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️ Feeding

Black Medaka Ricefish are omnivorous and easy to feed:

• High-quality micro pellets or fine flakes

• Frozen or live foods (baby brine shrimp, daphnia, cyclops)

• Occasional spirulina or vegetable-based foods

Feed small amounts 1–2 times daily.

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Tank Mates

Black Medaka are peaceful and social, best kept in groups of 6 or more.

Ideal companions:

• Other Ricefish varieties

• Small Rasboras

• Peaceful Tetras

• Shrimp and snails

Avoid:

• Aggressive fish

• Fin-nippers

• Large predatory species

⚠️ Behavioral Note: They prefer the upper water column, so avoid tank mates that aggressively dominate surface areas.

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Breeding

Breeding is very easy and often occurs naturally.

• Females briefly carry eggs before attaching them to plants or spawning mops

• Eggs hatch in 7–10 days, depending on temperature

• Fry accept infusoria, powdered fry food, or newly hatched baby brine shrimp

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Sexing / Identification

Males:

• Slender body shape

• Longer anal and dorsal fins

• More active courtship behavior

Females:

• Rounder body

• Shorter fins

• Often seen carrying eggs near the vent

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Interesting Fact

Japanese Ricefish (Oryzias latipes) are known for their incredible resilience and scientific importance — they were among the first vertebrates bred in space and remain a key species in genetic research.

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Reference: Bubbly Fish – Creating underwater wonders