Radenkou Medaka

Radenkou Medaka key facts

Care level

Beginner-friendly

Lifespan

2-3 years

Size

Up to about 4cm SL

Temperature

18〜28℃

Diet

Prepared medaka food, green water

Lighting

External luminescence appears on the back, so the fish is best viewed from above, and a dark container brings out the contrast between the white body and the sheen. The Medaka Web Encyclopedia recommends outdoor keeping and notes that summer sun raises water temperature sharply, suggesting shade such as a reed screen over half the container.

Diet & Nutrition

Commercial prepared medaka food is the staple, given in an amount finished within a few minutes. Leftovers decay and foul the water, so adjust the quantity. Green water rich in phytoplankton suits fry rearing.

Water Temperature & Quality

Slightly acidic to slightly alkaline water is considered ideal, and the water drifts toward acidic as keeping continues. Around one water change per week is the guideline, and because sudden shifts in temperature or pH cause stress, acclimatise new fish by floating the bag. FishBase records the wild water chemistry of this species as pH 7.0-8.0 and hardness 9-19 dH.

Tank Mates & Compatibility

A peaceful schooling fish, normally kept as a group of the same variety. One litre of water per fish is the guideline against overcrowding; overstocking causes poor growth, reduced breeding, oxygen shortage and water fouling.

Breeding

Outdoors the spawning season runs from about April to October, once water reaches 18C or above with 12-13 hours of daylight. For year-round indoor breeding, 25-28C water and over 13 hours of lighting are the guideline. Eggs hatch at a cumulative 250 degree-days, about 10 days at 25C.

Health & Notes

The length of the sheen varies between individuals, and fish whose light reaches the snout rank highest. Grading in a single container under consistent light makes the differences easier to read. Outdoors the fish become inactive and overwinter near the bottom as water cools, resuming activity in spring once daytime water exceeds 10C. A 0.3-0.5% salt bath is used for ailing fish, with water raised to no more than about 28C.

About Radenkou Medaka

Radenkou Medaka is a metallic-glow variety from the Shiro Kanno line, prized for the blue-white sheen reaching from the back toward the mouth. Calm-tempered and considered beginner-friendly to keep.

7 things to know before welcoming a Radenkou Medaka

1. 1Reading the Glow

   The extent of the metallic glow varies between individuals, and fish where the light reaches closer to the mouth are generally considered higher quality. Since the glow continues to develop as the fish matures, watching how it spreads is part of the ongoing enjoyment of keeping this variety.

2. 2Part of the Shiro Kanno Line

   Radenkou is a trade name given to metallic-glow individuals within the Shiro Kanno line, rather than a fully separate breed. This means it blends naturally when kept alongside other fish from the same line.

3. 3Beginner-Friendly Care

   This variety is considered easy to keep, making it a good choice even for first-time medaka keepers. That said, basic care such as regular water changes and temperature monitoring is still essential.

4. 4Expected Adult Size

   Adults typically reach a standard body length of up to about 4 cm. Provide enough space in the tank or outdoor container and avoid sudden changes in water quality as they grow.

5. 5Community Tank Compatibility

   Radenkou has a calm temperament and can be kept together with other medaka without issue. If you want to appreciate the glow clearly, keeping same-line individuals together makes it easier to compare differences in the light pattern.

6. 6Acclimation Before Introduction

   When moving fish into a new environment, acclimate them gradually to avoid sudden shifts in temperature and water chemistry. Feed sparingly right after arrival and return to a normal feeding schedule once the fish have settled in.

7. 7Daily Observation Tips

   The intensity of the glow can shift with light exposure, water quality, and nutrition. Making a habit of checking both health and glow condition during daily observation helps you catch changes early.

Frequently asked questions about Radenkou Medaka

Q.Can Radenkou Medaka be kept with other medaka?

A.Yes, they have a calm temperament and can be kept alongside other medaka. If you want to clearly appreciate the metallic glow, keeping same-line fish together makes the light patterns easier to compare.

Q.How long does it take for the metallic glow to fully develop?

A.The glow develops gradually as the fish matures, and the extent varies from one individual to another. Whether the light reaches close to the mouth depends on both the individual fish and its rearing environment.

Q.Is this variety suitable for someone keeping medaka for the first time?

A.Yes, it's considered a beginner-friendly variety that's easy to manage with basic care. Regular water changes and temperature monitoring are still necessary, though.

Q.How big do adults get?

A.Adults reach a standard body length of up to about 4 cm. Make sure the tank or outdoor container offers enough space for their size.

Q.What does the name "Raden" refer to?

A.It refers to raden, the traditional craft of inlaying iridescent shell, which the fish's glossy light is said to resemble. The name captures the blue-white shimmer that runs across its white body.

Useful tools for Radenkou Medaka care

Learn more about Radenkou Medaka in the encyclopedia

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