Pure Black Medaka

Pure Black Medaka key facts

Care level

Advanced

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. 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

Heritability of the small-eye trait is low and pure black pairings do not often give truly black fry, but continued line breeding and back-crossing raise the proportion. 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

Small pupils and weak eyesight make food hard to find, so feeding must be managed to reach every fish. The variety is more delicate than others and fixes poorly, which makes both keeping and breeding a job for experienced keepers.

About Pure Black Medaka

Pure Black Medaka keeps its deep black color even in white tanks, thanks to a small-eye trait that suppresses background response. First bred in 2001, it's among the earliest black medaka varieties, nicknamed "Kurobee."

7 things to know before welcoming a Pure Black Medaka

1. 1The Small-Eye Trait

   Pure Black Medaka carries a mutation known as "small eye," giving it noticeably smaller eyes than standard medaka. This trait suppresses the fish's natural background-response reflex, which normally shifts body color to match its surroundings.

2. 2Black Even in White Tanks

   Most medaka fade to a paler shade in white containers because of their background response, but Pure Black keeps its deep black color regardless of tank or substrate color. This makes it a striking choice for photography or display tanks.

3. 3Feeding Takes Extra Care

   Because their vision is limited, Pure Black individuals can take longer to locate food. Scattering food across several spots and feeding in calm water without strong currents helps make sure every fish gets enough to eat.

4. 4Choose Tankmates Carefully

   Pure Black can lose out at feeding time when housed with sharp-sighted, standard-bodied medaka. Keeping them with other small-eye varieties or calmer, slower strains tends to let them settle in and feed more comfortably.

5. 5Why It's for Experienced Keepers

   Pure Black is generally considered a variety for experienced keepers, since it calls for extra attention to its visual limitations and for husbandry that helps preserve its color. Keepers who already have some medaka experience tend to find it easier to bring out the variety's best qualities.

6. 6Grows to About 4cm

   Pure Black reaches a maximum standard length of around 4cm as an adult. Growth is gradual, shaped by consistent water changes and feeding rather than any sudden growth spurt.

7. 7Preparing Before You Bring One Home

   Before bringing a Pure Black home, make sure your tank's water quality is stable and free of sudden temperature swings. When choosing individuals, look for even, unblotched black coloring and natural, steady swimming.

Frequently asked questions about Pure Black Medaka

Q.Can beginners keep Pure Black Medaka?

A.Pure Black is generally considered a variety for experienced keepers. Its small-eye trait limits its vision, so feeding and tankmate selection need extra attention, and it's best introduced once you already have some medaka-keeping experience.

Q.Why does it stay black even in a white container?

A.Because the small-eye trait suppresses the background response, the reflex that normally causes medaka to lighten their color to match their surroundings. Its smaller eyes are what keep the black coloring stable.

Q.Is it okay to keep Pure Black with other medaka?

A.Mixing is possible, but Pure Black can lose out at feeding time when paired with sharp-sighted, standard-bodied medaka. Pairing it with other small-eye varieties or calmer strains tends to work better.

Q.What's the story behind the nickname "Kurobee"?

A.Pure Black's formal variety name is "Black Small Eye Medaka," and "Kurobee" is its common nickname. It was first bred in 2001 by Yukio Oba and is known as one of the earliest black-bodied medaka varieties.

Q.How big does Pure Black Medaka grow?

A.Pure Black reaches a maximum standard length of around 4cm as an adult. It grows gradually over time with regular water changes and feeding.

Useful tools for Pure Black Medaka care

Learn more about Pure Black Medaka in the encyclopedia

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