Medaka Variety Selection & Outdoor Keeping Guide — Popular Breeds to Breeding Basics

Choosing Medaka Varieties——Which One Should You Get?

There are now hundreds of medaka varieties in existence, and it's common to hear "I don't know which one to choose." Each variety possesses different charms——beautiful body coloration, fin shape, and radiance (sparkle). Here we introduce particularly popular varieties.

Miyuki Medaka A variety characterized by "body radiance" that shines along the back of the body. Depending on how the light passes through, there are various grades such as full-body and half-body versions. The white or blue-white body with silver light running through it is extremely beautiful, making it one of the most popular starter varieties. The price range is approximately 300-2,000 yen per pair, making it easy to obtain and ideal as a first variety medaka.

Sparkle Medaka A group of varieties with glittering sparkles (scale radiance) scattered across the entire body. "Black Diamond," "Sapphire," and "Orochi" are particularly popular among black sparkle varieties, with the density of sparkles tending to increase the price. Swimming in summer sunlight is especially striking, and they pair exceptionally well with outdoor cultivation.

Yōkihi Medaka A classic variety loved for a long time, distinguished by vibrant scarlet-red and orange body coloration. When cultivated outdoors with sunlight exposure, the body color develops a deeper hue. Hardy with strong reproductive capacity, it is one of the least demanding varieties for beginners.

Sanshoku (Three-Color) Medaka A variety where white, red, and black blend together like koi fish. The expression of the three colors varies greatly among individuals, with siblings displaying completely different patterns, combining collectibility with the joy of cultivation. Selection is difficult and considered suitable for intermediate to advanced keepers, though in recent years relatively stable three-color individuals have become more common.

Daruma Medaka A variety with a distinctly rounded, squat body shape. Due to their short form, their swimming is unique and endearing, providing relaxation simply from watching. However, due to their body type, they struggle to swim, and strong water currents are prohibited. Water temperature management also requires attention (Daruma body shape is more likely to develop at high water temperatures of 28℃ or above).

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Benefits and Preparation for Outdoor Cultivation

Unique Merits of Outdoor Cultivation

Outdoor cultivation closely resembles the medaka's natural living environment and offers many advantages over indoor cultivation.

• Nearly zero electricity costs: No heater or powerful lighting needed. Sunlight serves as both light and heat source
• Green water develops: Phytoplankton naturally proliferates, constantly supplying minute amounts of food and oxygen, creating an ideal aquatic environment
• Vibrant coloration: Exposure to sunlight activates pigments, often resulting in deeper coloration than indoor cultivation
• Breeding becomes easier: Natural daylight rhythm and water temperature changes trigger breeding, with spawning continuing unattended from spring through fall
• Space flexibility: Various containers can be utilized——water lily pots, foam boxes, planters——allowing cultivation in minimal spaces on balconies or yards

Necessary Preparation and Equipment

The items needed to begin outdoor cultivation are simple.

1. Cultivation container: Water lily pots (ceramic or plastic), tray boats, foam boxes, etc. A capacity of 20L or more is recommended (larger water volume ensures greater stability)
2. Substrate (optional): Small-grain red ball soil is commonly used. It promotes bacterial colonization and prevents water from becoming overly green
3. Aquatic plants and spawning beds: Pickerel rush, hornwort, etc. Creates a natural spawning environment and aids water purification
4. Water dechlorinator or aging water: Tap water cannot be used as-is. Either age water for 1-2 days or use liquid dechlorinator
5. Shade cloth (sun shade): Essential to prevent water temperature rise in midsummer. Water temperatures exceeding 35℃ are dangerous for medaka

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Water Temperature and Seasonal Management Points

Spring (March–May)——Beginning of the Breeding Season

Spawning begins when water temperature exceeds 18℃. Increase water change frequency to maintain water quality and install spawning beds. During this period, water temperature fluctuates significantly with weather, so caution is necessary regarding sudden drops (temperature changes of 5℃ or more). Medaka recovering from winter are weakened, so begin with small feeding amounts.

Summer (June–August)——Most Active Season·Heat Control Essential

On clear days with water temperatures of 25-28℃, spawning and feeding are most vigorous. Conversely, continuous direct sunlight can raise water temperature above 35℃. Covering approximately half of the container with shade cloth or shade netting to suppress water temperature rise is the most critical summer care. Additionally, water loss through evaporation is rapid, requiring regular water top-ups.

Fall (September–November)——Final Breeding Period·Preparation for Overwintering

As water temperature drops, spawning gradually decreases. When temperature falls below 15℃, begin reducing feeding, and stop feeding entirely below 10℃. Building sufficient fat reserves during this period is key to successful overwintering. Remove fallen leaves and dead grass to keep the container clean, and consider transitioning to a deeper container.

Winter (December–February)——Hibernation Period

When water temperature drops below 5℃, medaka enter a "hibernation" state, becoming motionless at the bottom of the container. During this period, never feed——it's an absolute rule. Uneaten food damages their organs. Keep water changes to a minimum, place a lid on the container or move it under shelter to prevent freezing. In most regions of Japan, medaka can survive winter without heating with adequate protection.

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Breeding Basics——From Eggs to Fry

Installing Spawning Beds

During active spawning seasons, females spawn in the morning with eggs dangling from their bellies as they swim. Install spawning beds (commercial sponge types or aquatic plants) to catch the eggs. Check spawning beds each morning and transfer attached eggs to a separate container.

Egg Management

Separate eggs from parent fish and manage them in a separate container. At 25℃ water temperature, they hatch approximately 10 days later (cooler temperatures require more time). Perform approximately 1/3 water changes daily until hatching, and promptly remove white, cloudy unfertilized or dead eggs to prevent fungal growth.

Raising Fry

Newly hatched fry (needle fish) are extremely tiny and cannot fit commercial prepared foods in their mouths. Utilize commercial powdered fry food, PSB (photosynthetic bacteria), or green water. Basic feeding is 3-5 times daily in small amounts. It's important not to house fry with parent fish until they reach over 1cm in length.

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Finding Variety Medaka at Br-Choku

Variety medaka are often rare specimens not seen at local home centers or tropical fish shops. Br-Choku allows you to purchase variety medaka directly from medaka breeders throughout Japan.

• Confirm the actual cultivation environment and water quality managed by breeders
• Rare varieties without normal supply routes and latest bred individuals are abundant
• Post-purchase cultivation consultation available directly from breeders
• Safe transactions for first-time users through escrow-style payment

If you're unsure "which variety should I start with," check actual listings in Br-Choku's medaka category. By viewing breeder profiles and cultivation environment comments, you can understand in advance who you'll be buying from, ensuring a safe introduction to your first variety medaka.