How difficult is it to keep Real Longfin Medaka?

Intermediate. This is an intermediate-level species. Some prior experience and knowledge of environmental management are recommended.

What is the ideal temperature for Real Longfin Medaka?

The ideal temperature for Real Longfin Medaka is 18〜28℃. Avoid sudden temperature changes and maintain a stable environment.

What is the lifespan of Real Longfin Medaka?

The average lifespan of Real Longfin Medaka is 2-3 years. With proper care and nutrition, they can live a long and healthy life.

How large does Real Longfin Medaka get?

Real Longfin Medaka typically reaches Up to about 4cm SL as an adult. Size may vary depending on care conditions and individual genetics.

What should I feed Real Longfin Medaka?

Real Longfin Medaka feeds on: Prepared medaka food, green water. Aim for a balanced diet with appropriate feeding frequency.

What is the typical price for Real Longfin Medaka?

The price of Real Longfin Medaka varies significantly depending on morph, size, and lineage. Check our market price page for the latest pricing information.

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Real Longfin Medaka

Intermediate

Oryzias latipes

An improved medaka in which every fin extends to at least 1.5 times its size while keeping its shape. Created in 2020 by Yoshinori Nakazato, it differs from hirenaga, whose extension is uneven, in that the caudal fin grows while staying triangular.

Difficulty

Intermediate

Temperature

18〜28℃

Lifespan

2-3 years

Size

Up to about 4cm SL

Diet

Prepared medaka food, green water

About

Real longfin is not a single variety but a fin-variation trait class in which every fin extends to at least 1.5 times its size while keeping its shape; the Medaka Web Encyclopedia lists it as the 38th of the recognised traits. It was created in 2020 by Yoshinori Nakazato, and the encyclopedia names hirenaga as the similar trait. The two differ in the shape of the extended part. Hirenaga extends unevenly, with the edge of the fin staying short while the centre grows longer, so on a standard body type the caudal fin takes on a rounded outline. Real longfin, by contrast, extends while preserving the fin's shape, so the caudal fin grows larger while staying a clean triangle. The trait combines with any body colour or pattern, so fish are usually named by adding Real Longfin to an existing variety name.

Source: Wikipedia (CC BY-SA 4.0)

Lifespan of the Real Longfin Medaka

The Real Longfin Medaka lives 2-3 years.

Size of the Real Longfin Medaka

The Real Longfin Medaka grows to Up to about 4cm SL.

Temperature & humidity for the Real Longfin Medaka

The ideal temperature for the Real Longfin Medaka is 18〜28℃.

Basic Info

Origin

Japan (trait created in 2020 by Yoshinori Nakazato)

Lifespan

2-3 years

Care Specifications

pH: 7–8
Hardness (GH): 9–19 dGH
Water Temp.: 18–28℃

PeacefulGroupBreeding: Moderate

Sources: Medaka Web Encyclopedia: Complete Medaka Care Guide / FishBase Oryzias latipes / Medaka Web Encyclopedia: Real Longfin, fin-variation trait 38/44

Morphs (Varieties)

The Japan Medaka Association's classification manual sorts varieties by traits that can be seen rather than by genotype, and does not set out how individual traits are inherited. Traits the manual explicitly says can be passed on and produced by selective, multi-generation breeding are listed as line-bred; the rest are grouped under Other.

Other

Real longfin (shape-preserving extension of all fins)

Sources: Japan Medaka Association: Variety Classification Manual, 5th ed. (Sep 2025) / Medaka Web Encyclopedia: Medaka Traits / Medaka Web Encyclopedia: Real Longfin, fin-variation trait 38/44 / Medaka Web Encyclopedia: Hirenaga (Matsui hirenaga), fin-variation trait 35/44

A curated selection of notable morphs. Inheritance modes are a breeding-planning guide; actual appearance varies with combos.

References & Sources

Edited & verified by: BreederDirect editorial team

The taxonomic, regulatory, and husbandry data on this page are compiled and verified against the authoritative primary sources below.

Primary sources

Taxonomy & Authority

Accepted name: Oryzias latipes (Temminck & Schlegel, 1846)

Breeder: 中里良則 (2020)

Authority databases: FishBase · GBIF · Medaka Web Encyclopedia: Real Longfin, fin-variation trait 38/44 · Japan Medaka Association: Variety Classification Manual

Nomenclature follows global taxonomic authority databases.

Regulations & Conservation Status

Not CITES-listedIUCN LC · Least Concern

Sources: CITES Appendices (species not listed) / FishBase (IUCN Red List: Least Concern, assessed 2018)

Regulations may change. Always verify the latest information with the relevant authorities.

Real Longfin Medaka Listings

Find listings for this species

🩺 Common diseases

Care Guide

Lighting

Because the fins grow larger while keeping their outline, viewing the fish from the side and checking the fin edge is the easiest way to judge the trait. Outdoors, summer sun raises water temperature sharply, so shade half the container with something such as a reed screen.

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

Elongated fins are easily damaged by obstructions or crowding, so keep the container uncluttered and the stocking light. 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

Because every fin grows large, swimming power tends to drop, so avoid strong flow and overcrowding. Tell the trait from hirenaga by the shape of the extended part: a caudal fin that stays triangular is real longfin, while one with a short edge and a rounded outline is hirenaga. 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.

Real Longfin Medaka

About

Lifespan of the Real Longfin Medaka

Size of the Real Longfin Medaka

Temperature & humidity for the Real Longfin Medaka

Basic Info

Care Specifications

Morphs (Varieties)

References & Sources

Taxonomy & Authority

Regulations & Conservation Status

Real Longfin Medaka Listings

Related Articles

🩺 Common diseases

For Breeders

Real Longfin Medaka

About

Lifespan of the Real Longfin Medaka

Size of the Real Longfin Medaka

Temperature & humidity for the Real Longfin Medaka

Basic Info

Care Specifications

Morphs (Varieties)

References & Sources

Taxonomy & Authority

Regulations & Conservation Status

Real Longfin Medaka Listings

Related Articles

🩺 Common diseases

Diet