Ryusho Hoshi Medaka

Ryusho Hoshi 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

Both hire-bi and black rim read clearly from the side, so a glass tank viewed from the side suits this variety. Outdoors, guard against summer overheating from direct sun.

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

Hikari-to-hikari pairings produce almost entirely hikari offspring, though bent spines are common in the form. 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 hikari form is prone to bent spines and hirenaga fins to splitting at the tips. Transparent scale is identified by the red gill covers showing through. Outdoors the fish become inactive and overwinter near the bottom as water cools, resuming activity in spring once daytime water exceeds 10C. A 0.3-0.5% salt bath is used for ailing fish, with water raised to no more than about 28C.

About Ryusho Hoshi Medaka

Ryusho Hoshi Medaka combines scarlet-orange transparent scales edged in black ("black rim") with long fins and a shimmering Hikari body — a striking variety suited to experienced keepers.

7 things to know before welcoming a Ryusho Hoshi Medaka

1. 1For Experienced Keepers

   Ryusho Hoshi is considered an advanced variety because its color and pattern are relatively difficult to maintain and breed true. If you're new to medaka keeping, it's a good idea to start with a hardier variety before taking this one on.

2. 2The Black Rim Pattern

   The defining trait of Ryusho Hoshi is the black outline, or "black rim," edging each scale. How strongly this pattern shows can vary between individual fish and change as they mature, so no two fish look quite alike.

3. 3Long Fins, Hikari Body

   This variety combines long, flowing fins with a shimmering Hikari body type. Because the fins themselves carry vivid color too, the fish is striking to watch from both the side and above as it swims.

4. 4Grows to About 4cm

   Adult standard body length reaches up to about 4cm. Choose a tank or container sized appropriately for the number of fish so they don't become overcrowded.

5. 5Water Temperature & Quality

   Medaka are generally hardy, but keeping the color and pattern looking their best means avoiding sudden swings in water temperature or quality. Around seasonal changes especially, smaller, more gradual water changes help reduce stress on the fish.

6. 6Watch for Crossbreeding

   If you want to preserve Ryusho Hoshi's distinctive pattern and body shape, avoid breeding it alongside other varieties in the same tank, as traits will mix. Keeping a separate breeding container helps maintain the line.

7. 7Getting Ready to Bring Them Home

   Before your fish arrive, prepare their tank with dechlorinated water, plants, and aeration so they have less to adjust to after transport. Once they arrive, acclimate them gradually to the new water rather than transferring them straight in.

Frequently asked questions about Ryusho Hoshi Medaka

Q.How difficult is it to keep Ryusho Hoshi Medaka?

A.Ryusho Hoshi is considered a variety for experienced keepers. Maintaining its color pattern and breeding it successfully both take some know-how, so it's best suited to those who already have some medaka-keeping experience.

Q.How big does Ryusho Hoshi Medaka grow?

A.Adults typically reach a standard body length of up to about 4cm. Since individual size can vary, choose a tank with enough room for your fish.

Q.Can Ryusho Hoshi be kept with other medaka varieties?

A.Housing them together in the same tank is fine, but breeding them alongside other varieties will cause the traits to cross, changing the pattern and body shape. If you want to preserve the line, keep a separate breeding container.

Q.Are there CITES restrictions on Ryusho Hoshi Medaka?

A.Ryusho Hoshi Medaka is not subject to CITES.

Q.Does the pattern change as Ryusho Hoshi grows?

A.How strongly the black-rim pattern shows can vary between individual fish and by growth stage. This individual variation is part of what makes each fish unique.

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