Mezen (Forward-Eye) Medaka

Mezen (Forward-Eye) 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 trait reads best from directly in front, so a setup that allows viewing from the front or the side as well as from above makes it easier to judge. 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

The angle varies widely and fish approaching 45 degrees are rated best, so selection is made looking at them head-on. Many lines combine mezen with telescope eye or transparent scales, so check which traits a line carries when acquiring fish.

About Mezen (Forward-Eye) Medaka

The Mezen Medaka features eyes angled forward, creating a striking face-to-face gaze from the front. Bred in 2007, it grows to about 4cm and suits intermediate keepers.

7 things to know before welcoming a Mezen (Forward-Eye) Medaka

1. 1Eye angle varies between fish

   Even within the same bloodline, the degree to which the eyes face forward differs from fish to fish. Individuals approaching a 45-degree angle are considered the most desirable, so it's worth checking the eye position from several angles before choosing your fish.

2. 2Best appreciated from the front

   The Mezen's unique look shows best when viewed from the front of the tank rather than from above. Setting up the aquarium so the front panel is easy to view will let you fully appreciate its distinctive expression.

3. 3Care basics match standard medaka

   Aside from the eye trait, the Mezen's body is essentially that of a standard medaka. Avoid sudden changes in water temperature or quality, and standard medaka care routines apply whether kept outdoors or indoors.

4. 4Considered suited to intermediate keepers

   The Mezen is generally regarded as suited to intermediate keepers. This isn't so much about day-to-day care difficulty as about having enough medaka-keeping experience to observe and appreciate the eye trait consistently.

5. 5The trait becomes clearer with growth

   Adults reach roughly 4cm at most. In young fry the forward eye angle can be hard to spot, so watching the trait become more distinct as the fish grows is part of the enjoyment.

6. 6Knowing its origin adds appreciation

   The Mezen was created in 2007 by breeder Kazuyoshi Kinoshita as a variety focused on eye positioning rather than body color. Knowing this unusual angle of selective breeding adds another layer of appreciation when viewing the fish.

7. 7Prepare your setup before bringing one home

   As with any medaka, careful acclimation and a stable water environment are essential when introducing a new fish. Set up your container and water in advance, and plan the introduction without rushing.

Frequently asked questions about Mezen (Forward-Eye) Medaka

Q.Can Mezen Medaka be kept together with other medaka varieties?

A.Since basic care is the same as for standard medaka, keeping them alongside other varieties is generally possible. However, if you plan to breed them, it's common to keep the same bloodline separate to preserve the eye trait.

Q.Do all individuals have their eyes facing forward to the same degree?

A.No, the angle varies from fish to fish. An angle approaching 45 degrees is considered the most desirable, but some individuals show a shallower angle, so it's best to check by viewing each fish from the front.

Q.When was the Mezen Medaka variety developed?

A.It was developed in 2007 by breeder Kazuyoshi Kinoshita. It's one of the relatively newer improved medaka varieties, created by focusing on the unusual trait of eye positioning.

Q.How large does the Mezen Medaka grow?

A.Adults grow to about 4cm at most (standard length), which is roughly the same size as typical medaka.

Q.Are there any legal regulations on keeping Mezen Medaka?

A.The Mezen Medaka is not subject to CITES. There is no need to worry about special regulatory procedures.

Useful tools for Mezen (Forward-Eye) Medaka care

Learn more about Mezen (Forward-Eye) Medaka in the encyclopedia

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