Mellor Medaka

Mellor 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

The divided fins read well from the side, so the variety also suits a side-viewed tank. 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

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

Some fish stop growing their fin rays partway, so select those whose fins still reach normal size. The trait is separated from samurai and choki by the fact that every fin is affected.

About Mellor Medaka

Mellor Medaka is a selectively bred variety whose fins split into multiple sections due to a missing fin membrane. First bred in 2013, it grows to about 4cm and suits intermediate keepers.

7 things to know before welcoming a Mellor Medaka

1. 1Defined by a Missing Membrane

   Mellor Medaka lack the thin membrane that normally joins the rays of each fin together. As a result, what would be a single fin instead spreads out into multiple sections, giving the fish a distinctive, delicate look.

2. 2Fin Expression Varies by Fish

   Through generations of selective breeding, some individuals now show the split-fin trait across every fin, though the extent still varies from fish to fish. Some show it only in the tail fin, others across several fins, making each individual worth examining on its own.

3. 3Suited to Intermediate Keepers

   Keeping the split fins looking their best benefits from some knowledge of water quality management and selective breeding, which is why this variety is generally considered suited to intermediate keepers. First-time medaka owners may want to get comfortable with basic care using a standard variety before taking one on.

4. 4Expected Adult Size

   As an adult, it reaches up to about 4cm in standard body length. Because the split fins spread out so much, it can visually appear larger than its actual body size.

5. 5Tank and Water Quality Care

   Because the split fins are thin and delicate, it's best kept in a tank without overly strong filter flow, with regular water changes to maintain good water quality. Avoiding sudden changes in water conditions helps keep the fins healthy.

6. 6Choosing Tankmates Carefully

   It has a fairly calm temperament and generally mixes well with other medaka varieties. However, since its split fins are delicate, it's best to avoid tankmates with a strong tendency to nip at fins.

7. 7What to Check Before Bringing One Home

   Before bringing one home, check that the fin splitting, body color, and swimming look natural and healthy. Since how the trait expresses itself varies from fish to fish, it's worth taking time to choose an individual whose features you like.

Frequently asked questions about Mellor Medaka

Q.What kind of variety is the Mellor Medaka?

A.It's a selectively bred medaka variety whose fins appear split into multiple sections because it lacks the membrane that normally joins the fin rays together. First developed in 2013, further selective breeding has since produced individuals showing the trait across every fin.

Q.Why do the fins appear split into multiple sections?

A.A medaka's fin is normally held together as a single sheet by a thin membrane. In the Mellor Medaka, this membrane is missing, so the fin rays spread apart and the fin appears divided into separate sections.

Q.How difficult is it to keep?

A.It's generally considered suited to intermediate keepers. Having some basic experience with medaka care makes it easier to manage fin condition and water quality.

Q.How large does it grow?

A.It reaches up to about 4cm in standard body length. Because its fins spread out so widely, it can look larger than its actual body size.

Q.Can it be kept with other medaka varieties?

A.It has a calm temperament and generally mixes well with other medaka varieties. That said, since its fins are delicate, it's best to avoid pairing it with fish known for nipping at fins.

Useful tools for Mellor Medaka care

Learn more about Mellor Medaka in the encyclopedia

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