Medaka Breeding Guide: Spawning to Fry Rearing

Medaka are relatively easy to breed, and with proper conditions they will spawn continuously from spring through autumn. Here's a detailed guide to the breeding process and fry care.

Basic Breeding Requirements

Medaka need the following conditions to begin spawning:

• Water temperature: 18°C or above (optimal 25–28°C)
• Photoperiod: 13+ hours of light per day (supplement with lighting indoors)
• Mature individuals: Adults at least 2–3 months old
• Nutritional condition: Fed sufficient high-quality food

Observing Spawning and Collecting Eggs

During spawning season, females can be observed carrying egg clusters on their abdomen each morning.

• Spawning substrate: Place water hyacinth or artificial spawning mops (commercially available)
• Egg collection: Gently pick eggs from spawning substrate by hand once daily
• Egg condition check: Transparent to pale yellow is normal. White, cloudy eggs are unfertilized or dead
• Separation from parents: Parents will eat eggs and fry, so always manage them in separate containers

Egg Incubation Management

Eggs take approximately 10–14 days to hatch (at 25°C, the accumulated temperature guideline is 250°C-days).

• Incubation container: Small containers, plastic cases, even PET bottles work
• Water: Use dechlorinated water or water from the original tank
• Methylene blue: Adding a dilute amount (half the specified concentration) helps prevent fungus
• Aeration: Gentle aeration aids water circulation
• Water changes: Change a small amount daily (10–20%)

Raising Fry (Needle Fry)

Hatched fry are extremely small; even after their mouths open, they survive on egg yolk for 2–3 days.

• Initial food: PSB, infusoria, or green water starting 2–3 days after hatching
• Commercial fry food: Feed powdered type 3–5 times daily in small amounts
• Water changes: Carefully suction debris from the bottom with a pipette
• Fry separation: Mixing fry of different sizes leads to cannibalism, so manage by size

Growth Timeline

• 1 week after hatching: Approximately 5mm at 25°C water temperature
• 1 month after hatching: Approximately 10–15mm
• 2–3 months after hatching: Approaching adult size and capable of breeding

Find Medaka on Bri-Choku

Selecting good parent fish is key to next-generation quality. Bri-Choku's medaka category features many listings with fixation rates and parent fish information, ideal for those wanting to enjoy breeding.