Bubble-Eye Medaka
Bubble-Eye Medaka are a striking variety of ornamental medaka distinguished by bubble-like swellings that form on the cornea around each eye. First recorded in 2008 by breeder Kubokouchi, this trait appears sporadically across various medaka lines, and "Hitomi," a Big-Eye Bubble-Eye strain, stands as the representative fixed lineage. Because the eye bubbles are delicate and easily damaged by rough decor or contact with other fish, this variety calls for careful tank setup and handling, making it best suited to experienced keepers. Adults reach roughly 4 cm in standard length, offering plenty of time to appreciate their unusual silhouette.
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Bubble-Eye Medaka key facts
- Care level
- Advanced
- Lifespan
- 2-3 years
- Size
- Up to about 4cm SL
- Temperature
- 18〜28℃
- Diet
- Prepared medaka food, green water
- Lighting
- The bubble over the eye reads well from the side, so the trait can be appreciated in 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
- 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 bubble is a swollen cornea and is easily damaged, so take care with container walls, decor and netting. The trait often appears by chance, and the number of fixed lines is limited.
About Bubble-Eye Medaka
A distinctive ornamental medaka whose cornea swells into bubble-like sacs. Discovered in 2008, with the Hitomi strain as its representative type — an advanced-keeper fish reaching about 4cm.
7 things to know before welcoming a Bubble-Eye Medaka
1Protect the Bubbles
The bubble-eye trait is extremely delicate, so avoid sharp decorations or coarse substrate in the tank. Choose driftwood and plants with smooth edges to reduce the risk of the bubbles rubbing against something and getting injured.
2Choose Tankmates Carefully
Fast-moving or aggressive fish can nip at the fragile eye bubbles, so avoid pairing them with boisterous tankmates. Other calm ornamental medaka make gentler companions.
3Handle With Care When Netting
A net can easily rupture the bubbles during water changes or transfers. Scoop the fish gently with a cup instead, keeping any contact away from the eye area.
4Watch Their Eyesight
As the bubbles enlarge, some fish have a reduced field of vision and may struggle to locate food. Observe each fish at feeding time to make sure it is getting enough to eat.
5Keep Water Quality Stable
The delicate eye tissue is sensitive to poor water quality, so regular water changes and reliable filtration are essential. Avoid sudden shifts in water parameters and aim for a stable environment.
6Bubbles Vary by Individual
The size and shape of the eye bubbles differ from fish to fish and change as they grow. Even siblings from the same spawn can develop noticeably different bubbles, which is part of the charm.
7Research Before You Bring One Home
This variety is considered suitable for experienced keepers, so it helps to learn the basics beforehand. Make sure you can commit time to daily observation and water quality care before bringing one home.
Frequently asked questions about Bubble-Eye Medaka
- Q.Is the Bubble-Eye Medaka suitable for beginners?
- A.The eye bubbles are delicate and easily damaged, so this variety is generally considered better suited to experienced keepers. It's a good idea to build up basic medaka-keeping experience before taking one on.
- Q.What happens if a bubble gets punctured?
- A.A punctured bubble will deflate and may not return to its original size. Keeping the water clean is important, as an open wound can also become a site for infection.
- Q.Can Bubble-Eye Medaka be kept with other fish?
- A.They can be kept with other calm, gentle fish, but aggressive or fast-swimming tankmates may nip at the bubbles. Choose companions carefully and watch how they interact.
- Q.How large do they grow?
- A.Adults reach roughly 4 cm in standard length. The size of the eye bubbles themselves varies between individuals.
- Q.Are there any legal restrictions on keeping this variety?
- A.This variety is not subject to CITES.
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