Han-Daruma (Semi-Balloon) Medaka

Han-Daruma (Semi-Balloon) Medaka key facts

Care level

Intermediate

Lifespan

2-3 years

Size

Between the standard and daruma body types (standard form up to about 4cm SL)

Temperature

18〜28℃

Diet

Prepared medaka food, green water

Lighting

Body shape is the point of interest, so the fish rewards viewing from above or from the side. Outdoors, shade half the container to avoid summer overheating.

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

Producing daruma fish requires water kept warmer than usual. Daruma-to-daruma pairings give few eggs and many infertile ones, so including han-daruma fish in the cross resolves both the egg count and the fertility. 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

The closer to the daruma form, the poorer the swimming and the more sensitive the fish is to changes in temperature and water quality. Females are prone to egg binding, and falling temperature or shifting water quality can bring on swim bladder trouble, so choose fish that swim level. 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.

About Han-Daruma (Semi-Balloon) Medaka

Han-Daruma Medaka is a body-shape classification between standard and Daruma medaka, valued for supporting Daruma breeding while offering a rounded body that's a bit easier to keep.

7 things to know before welcoming a Han-Daruma (Semi-Balloon) Medaka

1. 1A Body Shape, Not a Variety

   Han-Daruma Medaka isn't a named variety but a body-shape classification — shorter than a standard medaka but longer than a full Daruma. This intermediate form emerged through the process of stabilizing the Daruma body shape.

2. 2Key to Daruma Breeding

   The distinctive Daruma body shape often comes with lower spawning counts and fertilization rates. Han-Daruma medaka bridge that gap, making them essential for maintaining and improving Daruma breeding lines.

3. 3Best Suited to Intermediate Keepers

   Selecting and managing body-shape lines takes some hands-on experience, so this fish is generally considered suited to intermediate keepers. It helps to have some general medaka-keeping experience first.

4. 4A Build Between Standard and Daruma

   Adult size falls roughly between standard and Daruma medaka. Standard-body medaka typically reach up to about 4 cm, and Han-Daruma medaka have a somewhat more compact build than that.

5. 5A Swimming Style In Between, Too

   Compared to the somewhat awkward swimming of a full Daruma, Han-Daruma medaka move in a more natural way. Watching them lets you enjoy a blend of both standard and Daruma characteristics.

6. 6Expect Individual Variation

   Because body shape falls along a gradient from standard to Daruma, individual Han-Daruma medaka can vary noticeably in how compact their build is. It's worth checking each fish's actual shape before bringing it home.

7. 7Everyday Care Stays Simple

   Day-to-day care — water quality, feeding — follows the same basics as other medaka. No extreme measures are needed for this in-between body shape, but a stable, well-maintained environment helps it hold its form over time.

Frequently asked questions about Han-Daruma (Semi-Balloon) Medaka

Q.Is "Han-Daruma" an official variety name?

A.No, it's not a specific named variety — it's a body-shape classification. It describes a build between standard and Daruma medaka and can appear across several varieties and lines.

Q.Can beginners keep this fish?

A.Keeping one is possible, but selecting and maintaining body-shape lines benefits from experience, so it's generally considered suited to intermediate keepers. It helps to get comfortable with basic medaka care first.

Q.Why does its body shape differ from a full Daruma?

A.It's an intermediate form that appears during the process of breeding Daruma medaka. It helps offset the lower spawning counts and fertilization rates typical of the Daruma shape, making it valuable for breeding lines.

Q.How large does it grow?

A.Adult size falls roughly between standard and Daruma medaka. For reference, standard-body medaka typically grow up to about 4 cm.

Q.What happens if you breed two Han-Daruma medaka together?

A.Because body shape falls along a gradient, offspring won't necessarily match the parents' exact Han-Daruma build — some may lean closer to standard, others closer to full Daruma.

Useful tools for Han-Daruma (Semi-Balloon) Medaka care

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