Kaiji Medaka
Kaiji is a medaka that combines the Orochi body color, whose blackness holds up regardless of container color, with the panda eye and yellow pigment in the fins. The black body sets off the yellow fins nicely. Individuals with yellow dorsal and anal fins and a black tail fin are written with the kanji 改志 to tell them apart. It is a small medaka, and the variety is rated beginner-friendly. Like most medaka it is gentle, and comparing the fin coloring from one fish to the next is part of the fun of choosing one.
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Kaiji 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
- With no background adaptation it stays black even in white containers, where the yellow fins stand out.
- Breeding
- Names differ by how far the yellow extends; pair fish of the intended line, checking whether the tail is yellow or black.
- Tank Mates & Compatibility
- Peaceful and fine with other medaka of similar size. To keep the variety's traits, do not let it breed with other varieties in the same container.
- 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 Kaiji Medaka
Kaiji medaka: an Orochi-type black body with panda eyes and yellow fin pigment. Small and beginner-friendly. Care tips and what to know before you buy.
7 things to know before welcoming a Kaiji Medaka
1A Body That Stays Black
The Orochi-derived body color is known for staying black regardless of container color. That lets you choose a container for easy viewing rather than for color. The black body also makes the yellow in the fins stand out.
2What 改志 Means
Fish with yellow dorsal and anal fins and a black tail fin are written as 改志 to set them apart. It marks one specific fin-color combination among fish sold as Kaiji. Notation can differ from listing to listing, so check both the description and the photos.
3Check Each Fish
The amount of yellow in the fins and the color of the tail fin are worth comparing fish by fish. Checking the dorsal, anal, and tail fin colors in the photos and description helps avoid surprises. If anything is unclear, ask the breeder.
4Container and Placement
Adults are small, but a container with generous water volume tends to keep water quality steadier. Because the body color is not easily affected by the container, you can add plants and hiding spots to build a calm setup. Avoid spots with constant direct sun or sudden temperature swings.
5Acclimating at Arrival
After arrival, float the bag on the container's surface to match temperatures, then add small amounts of tank water to adjust the water chemistry. Sudden changes in water quality or temperature stress fish, so take your time. Feed lightly right after introduction and watch how the fish settle in.
6Feeding and Water Changes
Feed a medaka-formulated food in small portions, giving only what the fish can finish, to keep the water cleaner. Remove any leftovers. Change water in small amounts rather than all at once to limit swings in water quality.
7Tank Mates and Daily Checks
Medaka are gentle fish, so they generally do well with calm medaka of similar size. Avoid keeping them with large fish or fin-nippers. Checking swimming behavior, appetite, and fin condition each day helps you notice changes early.
Frequently asked questions about Kaiji Medaka
- Q.Can beginners keep Kaiji medaka?
- A.Kaiji is rated as beginner-friendly. What matters is sticking to the basics: avoid sudden changes in water quality or temperature, don't overfeed, and change water in small amounts.
- Q.How big do adult Kaiji get?
- A.There is little data on the adult size of this variety, and individuals vary. It is a small medaka.
- Q.How long do Kaiji medaka live?
- A.There is little documentation on this variety's lifespan, so we can't give a specific figure. Daily observation, stable water quality, and moderate feeding are the best foundation.
- Q.What is the difference between 改志 and Kaiji?
- A.Fish with yellow dorsal and anal fins and a black tail fin are written as 改志 to distinguish them. Notation can vary between listings, so check the description and photos.
- Q.Does container color change their color?
- A.Kaiji inherits the Orochi body color, which stays black regardless of container color. You can therefore choose a container based on how easy it is to observe and where you plan to place it.
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