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Ranchu Medaka
AdvancedNamed for resemblance to Ranchu goldfish — no dorsal fin and round body. A Daruma subtype with uniquely charming form. Poor swimmer, so careful tank mate selection.
Difficulty
Advanced
Temperature
15〜30℃（適温25〜28℃）
Lifespan
1-2 years
Size
2-3cm
Diet
Fine medaka pellets, brine shrimp
About
Ranchu medaka is named for its dorsal-fin-less, plump rounded body resembling the ranchu goldfish. Built on the daruma body type (short tail and trunk) with traits such as a missing dorsal fin, its distinctive, endearing form is the appeal. Small at 2–3 cm. Because the body is heavily modified, it swims somewhat poorly and slowly, so it should not be kept with strong, active swimmers but rather with equally gentle, low-mobility varieties. It tends to be sensitive to sudden temperature changes and cold, so keeping it in conditions that hold the optimal range (around 25–28°C) — possibly with a heater — is reassuring. Being less hardy than the standard type and somewhat harder to breed, it is considered a more advanced variety, favored by hobbyists who enjoy attentive care of its unique shape.
Basic Info
Origin
Japan (selectively bred variety)
Lifespan
1-2 years
Size
2-3cm
Temperature
15〜30℃（適温25〜28℃）
Diet
Fine medaka pellets, brine shrimp
Care Guide
Environment
Indoor keeping recommended. Weak current
Tankmates
Slow swimmer — keep with same variety only
Care Specifications
- pH
- 7–8
- Hardness (GH)
- 9–19 dGH
- Water Temp.
- 18–24℃
PeacefulGroupBreeding: Easy
Sources: FishBase: Oryzias latipes / Seriously Fish: Oryzias latipes
Morphs (Varieties)
改良メダカは体型×体色×柄×光(体内/体外)×鱗(透明鱗)×ラメ×ヒレ等のトレイト合成。掲載は当該品種を構成する確証トレイトのみで遺伝形式は確証のみ付与(不確実は省略)。遺伝形式は交配の参考。
RecessiveVisual only with two copies; one copy = het (carrier).
Daruma (short body)
Sources: JMA日本メダカ協会 改良メダカ品種分類マニュアル / 改良メダカWEB図鑑(medakazukan)
A curated selection of notable morphs. Inheritance modes are a breeding-planning guide; actual appearance varies with combos.
References & Sources
Edited & verified by: br-choku editorial team
The taxonomic, regulatory, and husbandry data on this page are compiled and verified against the authoritative primary sources below.
Taxonomy & Authority
Accepted name: (Temminck & Schlegel, 1846)
Synonyms: Aplocheilus latipes (Temminck & Schlegel, 1846), Poecilia latipes Temminck & Schlegel, 1846, Oryzias latipes latipes (Temminck & Schlegel, 1846)
Authority databases: FishBase · GBIF · 日本メダカ協会 品種分類マニュアル
Nomenclature follows global taxonomic authority databases.
Ranchu Medaka Listings
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