How to Breed and Select Ramé Medaka | Tips to Maximize Their Brilliance

Ramé medaka are beautiful fish whose scales shimmer with iridescent colors, leading the recent medaka boom as a highly popular variety. However, the brilliance of ramé is greatly influenced by husbandry conditions and genetics, so special techniques are needed to bring out their maximum beauty. This article explains how to breed ramé medaka and the key points of selection.

The Mechanism of Ramé Expression

The brilliance of ramé medaka is created by guanine crystals (iridophores) located on the surface of their scales reflecting light. While ordinary medaka also possess iridophores, ramé medaka have these cells specially developed, causing each individual scale to shimmer and shine. Ramé types are broadly divided into "normal ramé" and "body-light ramé." Normal ramé sparkles in point-like patterns on individual scales, while body-light ramé shines in a band along the dorsal line. In recent years, individuals called "full-body ramé," whose entire bodies are densely covered in ramé, have become extremely popular. Ramé color is also diverse, showing silver, gold, blue, green, and other brilliant colors depending on the angle of light and observation. While the quantity and quality of ramé are largely determined by genetics, the degree of expression also changes depending on husbandry conditions.

Husbandry Environment to Enhance Ramé

To maximize the brilliance of ramé, careful attention to husbandry conditions is essential. Tank color should be black as a standard. When bred in black containers, medaka undergo "background adaptation," causing their body color to deepen and making the ramé contrast stand out distinctly. In white containers, body color fades and ramé becomes less noticeable. Water temperature between 25–28°C is optimal for ramé expression; temperatures that are too high or too low tend to dull the ramé brilliance. Sunlight has a positive effect on ramé coloration, but prolonged direct sunlight raises water temperature excessively, so a location receiving sun only in the morning is ideal. Tank stocking density should be kept relatively low; ensure at least 2 liters of water per individual fish. Overcrowding causes stress and suppresses ramé expression. Feed high-protein specialized food 2–3 times daily to promote growth.

Key Points of Selective Breeding

To improve ramé medaka quality, selective breeding across multiple generations is essential. The basic principle of selection is to pair individuals with abundant ramé, but there are several considerations. Beyond merely counting ramé, also evaluate ramé size, distribution balance, and brightness intensity as selection criteria. Individuals with evenly distributed ramé from head to tail base are ideal. Selection should be performed at 2–3 months post-hatching, when ramé tendencies are somewhat visible. Since some individuals develop more ramé as they grow, multiple rounds of selection are desirable. In pairings, introducing ramé medaka from different lineages to refresh the genetic line is also important. Continued breeding from the same lineage can result in inbreeding depression, weakening the body and potentially reducing ramé quality. Individuals culled from selection are still sufficiently beautiful for ornamental purposes and can be enjoyed in separate tanks.

Popular Ramé Varieties and Their Characteristics

Many ramé medaka varieties exist. "Sapphire" features blue ramé scattered across the entire body, its contrast with the black body color beautifully resembling gemstones and boasting high popularity. "Yozakura" (Night Cherry Blossom) is a variety with black and orange body coloration adorned with ramé, characterized by a vibrant appearance. "Amber Ramé" displays an amber-colored body with shimmering gold ramé, offering a warm and elegant beauty. "Tri-color Ramé" is a luxurious variety combining red, white, and black coloration with ramé, evoking the aesthetic of koi. "Ulysses" combines bluish body-light with ramé for a fantastical effect. Price varies significantly based on ramé quality; common individuals start from a few hundred yen, while carefully selected full-body ramé specimens can command tens of thousands of yen.

Handling Culled Individuals from Selection

What to do with individuals culled during selection is a problem faced by all hobbyists engaged in breeding. Several options are available:

• Giving to acquaintances or friends: Sharing with friends interested in goldfish is the most ideal option
• Having pet shops adopt them: Some shops will take them free of charge
• Exchange or transfer through hobbyist clubs: Regional medaka clubs sometimes facilitate exchanges between members
• Finding adoptive homes through SNS and online communities: Recruit foster homes through goldfish enthusiast communities

While selection is an unavoidable practice for developing quality individuals, remember that culled fish also have life, and do your best to handle them responsibly.

Choosing Ramé Medaka on BreederDirect

Ramé medaka are difficult to evaluate for brilliance quality from photographs alone. On BreederDirect, you can purchase directly from breeders who take care in selecting ramé and verify information about parent stock and lineage background. Choosing breeders who provide detailed explanations about ramé quantity and quality makes it easier to obtain individuals meeting your expectations. Since you can also receive advice on selection techniques and husbandry conditions, those pursuing ramé brilliance are encouraged to take advantage of the service.