Starting a Medaka Side Business — From Breeding to Sales

Medaka breeding as a side business has recently garnered significant attention as an activity that combines hobby and profit. Starting from a small space, requiring relatively modest initial investment, and with high reproductive capacity, medaka are an ideal beginner's organism for side-business breeding. However, conducting sales on a serious scale requires knowledge of legal procedures, quality management, sales strategies, and more.

The Appeal and Reality of Side-Business Breeding

The reasons medaka breeding is gaining popularity as a side business are clear. The ability to start in a small space, short breeding cycles (approximately 10 days from egg-laying to hatching), and the ability to sell popular varieties at premium prices are the main attractions. Improved medaka can sell for several thousand yen per pair, and rare varieties can fetch tens of thousands of yen per individual.

On the other hand, it's important to understand that achieving stable income takes time. Consistently producing high-quality individuals requires a minimum of 1–2 years of experience, and building sales channels and accumulating trust also takes time. Unrealistic expectations of "easy profit" should be avoided.

Required Equipment and Initial Investment

Here's an overview of equipment necessary for side-business-scale medaka breeding.

Breeding containers: NV boxes and plastic containers are standard. Since you manage different varieties separately, you'll need at least 10–20. A 13-liter NV box typically costs ¥500–800 each.

Containers for breeding stock: Breeding stock that maintains varieties should be managed carefully in slightly larger containers. Prepare 40–60-liter plastic containers for each variety.

Fry rearing containers: Numerous containers are needed to raise hatched fry. Containers from 100-yen shops or buckets can also be used.

Air pump and air stone: Necessary for indoor overcrowding. Using a splitter valve allows one pump to aerate multiple containers.

Feed: Prepare artificial pellets for adult fish, powdered feed for fry, and live feed (Tetrahymena, PSB, Daphnia, etc.).

Initial investment estimate: Equipment typically costs ¥30,000–50,000, with breeding stock purchase at ¥20,000–100,000. Acquiring quality breeding stock of popular varieties represents the largest investment.

Variety Selection Strategy

Choosing varieties with sales in mind is key to success.

Stable popular varieties: Mikiyoshi medaka, Yangui medaka, and three-color medaka have consistent popularity and stable demand. However, high supply often leads to price competition.

Trend varieties: Newly released varieties can be sold at premium prices, but there's a risk of price drops when trends fade. Continuously checking the latest variety information and understanding market trends is essential.

Niche varieties: Obscure or long-established fixed varieties have limited demand but also less competition, allowing for stable sales. Specializing in specific varieties builds expertise appeal.

Emphasize fixation rate: When selling, you have a responsibility to consistently supply individuals matching the variety name's quality standards. Low fixation rates result in more culled individuals and reduced efficiency.

Breeding and Rearing Tips

Key points to maximize breeding efficiency:

Promoting spawning: Water temperatures of 25–28°C and light periods of 13+ hours encourage active spawning in medaka. Outdoor breeding naturally occurs from April to September. Year-round breeding is possible indoors using lighting, but watch for parent fish exhaustion.

Egg collection and hatching: Collect eggs attached to spawning substrates daily and transfer them to water with diluted methylene blue. Methylene blue effectively prevents egg fungus. At 25°C, eggs hatch in approximately 10 days; at 28°C, approximately 8 days.

Fry rearing: The survival rate of newly hatched fry (naishi) significantly affects breeding efficiency. The first two weeks are critical, requiring multiple daily feedings of powdered feed, Tetrahymena, or PSB (photosynthetic bacteria). Maintaining green water (phytoplankton) in containers allows fry to continually consume microorganisms, improving survival rates.

Culling: Once fry reach approximately 2cm in length, cull them based on body shape and color. Divide into breeding stock candidates, sales individuals, and culls. Cull individuals can also be sold inexpensively as mixes.

Building Sales Channels

Determining where to sell your medaka is an important consideration.

Online auctions and resale apps: Yahoo Auctions and Mercari are the most accessible sales channels. While listing requires effort, you can reach buyers nationwide. Photography technique and description quality significantly impact sales, requiring careful attention.

In-house direct sales websites: For serious sales, consider establishing your own website or social media account. Sharing medaka photos on Instagram or X (formerly Twitter), gaining followers, and directing them to online sales is effective.

Event sales: Medaka instant sales and exchange events provide face-to-face sales opportunities. Seeing direct customer reactions is invaluable information for gauging variety popularity.

Selling on Br-Choku: Br-Choku is a direct-sales platform for breeders with established sales systems. Use a trustworthy sales channel without the hassle of building your own e-commerce site.

Legal Considerations

Continuous medaka sales require legal procedures.

Animal dealer registration: Selling medaka repeatedly for profit requires registration as an animal dealer (sales business) with your prefectural government. Registration requires appointing an animal handler in charge, typically requiring relevant qualifications or practical experience.

Specified Commercial Transactions Act display: Selling online requires notations per the Specified Commercial Transactions Act (business name, address, phone number, return policy, etc.).

Tax filing: If side-business income exceeds ¥200,000 annually, tax filing is required. Net income after deducting expenses like feed, containers, and shipping costs is subject to taxation. Keep receipts and invoices.

Packing and Shipping Expertise

Live shipping requires careful attention. The standard method is double plastic bags filled with oxygen, placed in styrofoam boxes. Add ice packs in summer and heat sources in winter for temperature control. Aim for next-morning arrival as standard; minimizing transit time ensures fish safety.

Start Selling on Br-Choku

To begin side-business medaka breeding, your first step is obtaining quality breeding stock. On Br-Choku, you can directly purchase breeding stock from breeders with high fixation rates and receive breeding advice. As you grow as a breeder, you can also sell on Br-Choku.