Tainaikou (Inner-Glow) Medaka

Tainaikou (Inner-Glow) Medaka key facts

Care level

Intermediate

Lifespan

2-3 years

Size

Up to about 4cm SL

Temperature

18〜28℃

Diet

Prepared medaka food, green water

Lighting

Because the glowing layer forms a horizontal plate, the light can only be seen from above. Both viewing and selection are done looking down into the container, and the trait is hard to appreciate in a side-viewed tank. Outdoor containers viewed from above suit it best.

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 extent of the glow varies widely, and fish whose light runs from the dorsal fin to the pectoral fins are rated highest. The glow appears mainly on the white and blue body colours inherited from miyuki, and is hard to see on others. Peritoneal glow and full-body tainaikou are classed as separate traits.

About Tainaikou (Inner-Glow) Medaka

A selectively bred medaka with a pale blue-white glow inside its body, visible only from above. Suited to keepers with some experience, it offers a glow expression distinct from external-glow types.

7 things to know before welcoming a Tainaikou (Inner-Glow) Medaka

1. 1View the Glow from Above

   Because the inner glow forms as a flat, horizontal layer, it can be hard to see from the side of the tank. Using a shallow container suited to top-down viewing, or arranging the setup so you can look straight down, helps you fully appreciate this variety's distinctive shine.

2. 2Best Suited to Experienced Keepers

   This variety is generally considered best suited to keepers with some prior experience. Those already comfortable with the basics of medaka care — water quality management, water changes, and feeding — will find it easier to keep consistently.

3. 3Stays Compact Even as an Adult

   Even as adults, these fish stay compact, reaching a standard length of up to about 4 cm. While this makes them manageable in relatively small containers, overcrowding can quickly degrade water quality, so choose a container size appropriate to the number of fish.

4. 4How It Differs from External-Glow Medaka

   External-glow (taigaikou) medaka show a streak of light along the back, while Tainaikou medaka carry a light layer inside the body that's only visible from above. This is a key point of visual classification worth keeping in mind when choosing between the two.

5. 5Base Colors Are White and Blue

   The base body colors that appear are white and blue. Since individual fish can vary in how the glow presents and in its intensity, it's a good idea to carefully check actual photos and the top-down appearance before deciding to bring one home.

6. 6Avoid Sudden Water Changes

   As with medaka in general, sudden shifts in water quality or temperature can be stressful. When changing water, keep differences small and take care to properly acclimate the fish before introducing them.

7. 7Prepare the Container and Environment First

   Setting up the container, water, and food in advance makes for a smoother start. Since this variety is best appreciated from above, it's worth thinking ahead about where you'll place the container and what shape best suits top-down viewing.

Frequently asked questions about Tainaikou (Inner-Glow) Medaka

Q.Is the Tainaikou Medaka subject to CITES?

A.The Tainaikou Medaka is not subject to CITES. There's no need to worry about any CITES-related procedures for this variety.

Q.Can the inner glow be seen from the side?

A.Because the glow forms as a flat, horizontal layer, it's generally easiest to see when viewed from above. From the side, the glow can be difficult to make out.

Q.How is it different from external-glow medaka?

A.External-glow medaka show light along the back, while Tainaikou medaka develop a glowing layer inside the body. Because the location and appearance of the glow differ, they're classified as distinct lines.

Q.Can beginners keep this variety?

A.This variety is generally considered suited to keepers with some experience. It tends to be easier to keep consistently once you're already comfortable with the basics of medaka care.

Q.How large does it grow as an adult?

A.Even as an adult, it stays compact, reaching a standard length of up to about 4 cm. This makes it a manageable size for relatively space-saving containers.

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