Ogawa Black Medaka
Ogawa Black is an improved medaka variety valued for holding its deep black coloration no matter the surroundings. Most medaka shift their body color in response to their tank's substrate or background — a trait known as background adaptation — but Ogawa Black shows almost none of this response, so its black stays consistent day after day. It was developed by selecting individuals with unusually dense black pigment cells from a low-yellow, high-black purple-blue lineage, with the variety established in 2009. Following Pure Black, it is recognized as one of the notable black-bodied medaka lines. Its body shape is the standard, unexaggerated normal-eye type, so keepers enjoy a classic medaka silhouette rendered in a striking, stable black.
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- Body Type
- Scale Type
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Ogawa Black 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
- With no background response the black holds even in a white container, so colour can be judged whatever the container. Fish that do respond turn grey in about five minutes in a white container, so use one for identification. The Medaka Web Encyclopedia recommends outdoor keeping and suggests shading half the container in summer.
- 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
- For selection, move the fish to a white container and confirm the colour does not turn grey. The black body colour overlaps with purple blue, and there is no firm line between it and background-responsive black, so the judgement is left to individual keepers.
About Ogawa Black Medaka
Ogawa Black is an improved medaka valued for holding deep black color regardless of tank surroundings, bred by selecting black-pigment-rich fish from a purple-blue lineage. Explore care tips and FAQs.
7 things to know before welcoming a Ogawa Black Medaka
1No Background Adaptation
Most medaka lighten or darken their coloring to match their tank's substrate and background, a response called background adaptation. Ogawa Black shows almost none of this, so its black stays vivid even if you change the tank's layout.
2Best for Intermediate Keepers
Ogawa Black is generally recommended for intermediate keepers. Keeping water quality and temperature stable, along with regular water changes, helps maintain both its color and overall health.
3Adult Size and Tank Space
Adults reach up to about 4 cm in standard body length. A small container works for keeping a single fish, but plan for more water volume if you're keeping several or breeding them.
4A Selectively Bred Black Line
Ogawa Black was created by selecting individuals with especially dense black pigment cells from a purple-blue lineage that already ran low on yellow pigment and high on black. It's known as one of the notable black medaka varieties, developed after Pure Black.
5Classic Body Shape
It carries no special body-shape modifications such as daruma or telescope eyes — its body and eye size stay close to those of wild-type medaka. That keeps a natural silhouette alongside the deep black coloring.
6Color Shifts Can Signal Stress
Because its color doesn't fluctuate with the background, a dulling or fading black — especially alongside reduced appetite or sluggish movement — is easier to spot as a possible sign of poor water quality or health issues. Regular observation helps you catch changes early.
7Acclimate Carefully Before Bringing Them Home
When introducing new fish, take time to acclimate them gradually to your tank's temperature and water chemistry. Reducing the stress of transport and environmental change supports their health afterward.
Frequently asked questions about Ogawa Black Medaka
- Q.What makes Ogawa Black distinctive?
- A.Its defining trait is holding a deep black color with almost no background adaptation, so its color stays consistent regardless of the tank's surroundings. It was developed by selecting individuals with dense black pigment cells from a purple-blue lineage.
- Q.Is this variety suitable for beginners?
- A.Ogawa Black is generally considered suited to intermediate keepers. Some experience with routine water quality management and water changes helps keep its color and health stable.
- Q.How big do adults get?
- A.Adults reach up to about 4 cm in standard body length. Plan your tank and water volume with this adult size in mind.
- Q.Can Ogawa Black be kept with other medaka?
- A.Calm-tempered medaka varieties can generally be housed together. That said, if you want to preserve its color or keep the line pure for breeding, keeping it alone or in a separate container is recommended.
- Q.Is Ogawa Black subject to CITES?
- A.Ogawa Black is not subject to CITES.
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