Ruby-Eye Medaka

Ruby-Eye Medaka key facts

Care level

Beginner-friendly

Lifespan

Few reliable data

Size

About 3-4 cm (wild medaka reach up to 4 cm SL: FishBase)

Diet

Omnivore (floating prepared foods, live foods such as daphnia)

Container & Tank

From afar the eyes look normal, so a glass tank viewed up close from the side suits it.

Breeding

Derived from albino lines, colours tend to be white or cream; choose breeders with clearly red eyes.

Health & Cautions

The red eyes are hard to tell from normal eyes at a distance, so check the actual fish up close when buying.

Diet & Feeding

Give floating food that is eaten within 3-5 minutes: at least twice a day in summer, once a day in spring and autumn, and little or none outdoors in winter.

Cautions

Never release ornamental medaka into rivers, ponds or paddies; hybridisation causes genetic pollution of wild medaka.

About Ruby-Eye Medaka

Ruby-Eye Medaka have wine-red, near-black eyes that keep their color from every angle, unlike grape-eye types. Small and beginner-friendly.

7 things to know before welcoming a Ruby-Eye Medaka

1. 1A Name for an Eye Trait

   Ruby-eye is not a strain name but a trait name for wine-red, near-black eyes. Body color and shape differ from line to line, so two fish sold as ruby-eye can look quite different. Check the photos and description for body color as well.

2. 2Not the Same as Grape-Eye

   Grape-eye (color-change) medaka show a different eye shade depending on the viewing angle. Ruby-eye medaka keep the same eye color from every angle. Because the names are easy to mix up, look at photos taken from more than one angle if they are available.

3. 3Beginner-Friendly Care

   Ruby-eye medaka are rated beginner-friendly, and basic medaka care applies. They can be kept in a tank or an outdoor container, so you can choose whichever suits your space.

4. 4Avoid Harsh Direct Sun

   Because the trait comes from albino-type lines, it is a good precaution to avoid spots where strong direct sun hits the fish for long periods. Even in an outdoor container, floating plants or a sunshade create shaded areas that give them somewhere to retreat.

5. 5Choose Tank Mates Carefully

   Ruby-eye medaka are small and peaceful. Avoid keeping them with aggressive fish or fish large enough to swallow them. If you want tank mates, choose gentle species that will not chase or eat them.

6. 6Acclimate Slowly

   When you bring them home, float the bag on the water to even out the temperature, then add tank water a little at a time. Treat tap water with a dechlorinator, and avoid sudden changes in water quality or temperature.

7. 7Lifespan Data Is Limited

   There is little reliable information on the lifespan of ruby-eye medaka, so we can't give a specific number of years. Daily observation and careful, steady care are the best foundation for keeping them long term. If you breed them, moving plants or spawning mops that carry eggs to a separate container reduces the chance of the parents eating them.

Frequently asked questions about Ruby-Eye Medaka

Q.How is Ruby-Eye different from grape-eye?

A.Ruby-eye medaka have wine-red, near-black eyes that stay the same color from every angle. Grape-eye (color-change) medaka are distinguished by eyes that appear to shift color depending on the viewing angle.

Q.Is Ruby-Eye the name of a breed?

A.Not exactly. It is a trait name for the wine-red, near-black eye color, which is said to derive from albino-type lines. Body color and shape can differ from one line to another.

Q.Can beginners keep Ruby-Eye Medaka?

A.Yes, they are rated beginner-friendly. Following standard medaka care, such as dechlorinating tap water and feeding small amounts at a time, works in either a tank or an outdoor container.

Q.How large do they get?

A.There is little data on the adult size of this variety, and individuals vary. It is a small medaka, easy to keep in a compact tank or container.

Q.What should I check before buying?

A.Use the photos and description to check that the eye color stays the same from every angle, and to confirm the body color and line. Ask the seller about anything unclear, including the water conditions and rearing environment they use.

Useful tools for Ruby-Eye Medaka care

Learn more about Ruby-Eye Medaka in the encyclopedia

More in this category