How difficult is Ryokukou to keep?

Ryokukou is considered a variety for intermediate keepers. The basics of care are similar to other medaka, but bringing out the green tone of its body glow well calls for attention to water quality and lighting.

How big does Ryokukou grow?

Adults reach roughly 3–4 cm in length. That's a similar size to most medaka varieties, making it easy to plan tank space around.

How long does Ryokukou live?

Its lifespan is generally around 2–3 years. Keeping an eye on water temperature and your fish's daily health helps it live well for the long term.

Can Ryokukou be kept with other medaka?

Yes, it has a calm temperament and generally mixes well with other medaka. Just avoid overcrowding, since a dense tank can affect both water quality and how well the coloration shows.

Where does the name "Ryokukou" come from?

Unlike the silvery-white body glow typical of most medaka, Ryokukou displays a distinctly greenish shimmer, which is what gives the variety its name. That unusual coloration, combined with its rarity, has made it popular among collectors.

Ryokukou (Green Light)

Ryokukou, meaning "Green Light," is an uncommon medaka variety known for the greenish tint of its body glow — a striking departure from the silvery-white shimmer most medaka display. Depending on the light and angle, its cool green luster gives the fish a distinctive, eye-catching presence unlike other varieties. Its temperament is calm, and it generally gets along well with other medaka. Because bringing out its coloration well calls for attention to water quality and lighting, Ryokukou is considered better suited to intermediate keepers; adults reach about 3–4 cm and typically live around 2–3 years. As a relatively rare variety, it has a devoted following among collectors interested in breeding and coloration.

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Ryokukou (Green Light) key facts

Care level: Intermediate
Lifespan: 2-3 years
Size: 3-4cm
Temperature: 5〜30℃
Diet: Medaka pellets, daphnia
Container: Black top-viewing container shows green external light best
Temperature: 5-30°C (optimal 20-28°C)
Sunlight: Natural light makes green shimmer more vivid
Breeding: Ryokukou trait has slightly lower inheritance — selection important
Notes: Rare variety — may be difficult to obtain

TraitsModified medakaGreen external lightRareCollectorExternal light

About Ryokukou (Green Light)

Ryokukou is a rare medaka variety with a distinctive greenish body glow, unlike the usual silvery-white shimmer. Suited to intermediate keepers, adults reach 3–4 cm and live about 2–3 years — here's what to know before choosing one.

7 things to know before welcoming a Ryokukou (Green Light)

1Suited to Intermediate Keepers
Ryokukou is cared for much like other medaka in the basics, but bringing out the green tone of its body glow well calls for attention to water quality and lighting. It's a good idea to gain some medaka-keeping experience before taking one on.
2How the Glow Appears
The body glow that gives Ryokukou its name changes appearance depending on the angle and quality of light. Viewing the tank from above (a "top view") tends to show off its greenish shimmer most clearly.
3Compatibility with Others
Ryokukou has a calm temperament and generally does well alongside other medaka. That said, avoiding overcrowding and keeping water quality stable helps preserve its coloration.
4Adult Size
Ryokukou typically reaches about 3–4 cm as an adult. Keep tank or biotope stocking density reasonable for the space you have available.
5Lifespan and Long-Term Care
Ryokukou's lifespan is generally around 2–3 years. Watching for seasonal water temperature swings and checking on your fish's health day to day both matter for a long relationship with them.
6Its Rarity
Ryokukou is a relatively rare variety. Because opportunities to find one are fewer than with more common varieties, it draws particular interest from collector-minded keepers.
7Getting Ready Beforehand
Before bringing one home, set up your tank and filter and allow time for the water to cycle and stabilize. Choosing a spot with moderate light but no direct sun also helps bring out Ryokukou's body glow.

Frequently asked questions about Ryokukou (Green Light)

Q.How difficult is Ryokukou to keep?: A.Ryokukou is considered a variety for intermediate keepers. The basics of care are similar to other medaka, but bringing out the green tone of its body glow well calls for attention to water quality and lighting.
Q.How big does Ryokukou grow?: A.Adults reach roughly 3–4 cm in length. That's a similar size to most medaka varieties, making it easy to plan tank space around.
Q.How long does Ryokukou live?: A.Its lifespan is generally around 2–3 years. Keeping an eye on water temperature and your fish's daily health helps it live well for the long term.
Q.Can Ryokukou be kept with other medaka?: A.Yes, it has a calm temperament and generally mixes well with other medaka. Just avoid overcrowding, since a dense tank can affect both water quality and how well the coloration shows.
Q.Where does the name "Ryokukou" come from?: A.Unlike the silvery-white body glow typical of most medaka, Ryokukou displays a distinctly greenish shimmer, which is what gives the variety its name. That unusual coloration, combined with its rarity, has made it popular among collectors.