Breeding the medaka
Easy and prolific: eggs are fertilised as a single mass, hang from the female's vent for a while, then are brushed off singly or in small clumps onto plants or other media.
Step by step
Keep a group of 6+ adults.
A small tank or tub with plants or yarn.
Warm water and long light hours.
Females in good condition spawn a batch every few days or even daily; eggs hatch in about 1-3 weeks depending on temperature.
Fry feed on infusoria then powdered foods.
- Not removing eggs
- Cold water
- Overcrowding
Male or female
Males have larger, convex dorsal and anal fins with long filament-like rays and a slightly slimmer body; females have smaller, non-convex fins and carry egg clusters from the vent after spawning.
Can I breed it in my tank?
- Use a separate small tank with a sponge filter and spawning mops, so the eggs aren't eaten.
- Good for a first breeding project.
Day-by-day plan
Typical for egg scatterers
- 14 days beforeCondition the parents
Feed live or frozen food twice a day. Keep males and females apart if you can.
- Day 0Spawning
Eggs are scattered over mops or fine plants, often at first light. Remove the parents straight after.
- Day 1Eggs hatch
Most eggs hatch in 1–2 days. Keep the tank dim and remove white (fungused) eggs.
- Day 4Free swimming, first food
Fry use up the yolk and start swimming. Feed infusoria or liquid fry food several times a day.
- Day 8Baby brine shrimp
Switch to newly hatched brine shrimp or microworms. Start small, daily water changes.
- Day 21Crushed flake
Add finely crushed flake. Sort fry by size so the big ones don't eat the small ones.
- Day 60Ready to move
Most small fish reach about 2 cm in 2–3 months and can join the main tank.
A general guide for this breeding type. Days change with temperature and species.
Simulator: guided
Feed live or frozen food twice a day. Keep males and females apart if you can.
Simulator: try it yourself
Set up a virtual breeding tank and see what would likely happen.
- Without live or frozen food the parents aren't in breeding condition.
An educational estimate from the breeding rules, not a promise.