Breeding

Betta Gillfriend care rules: one betta per tank. Mirror or flare practice: one 2-minute session a day, with at least 2 rest days a week. Train: up to 10 minutes a week.

Watching a male betta build a nest and care for his eggs is amazing. But breeding bettas is a big commitment that goes well beyond one exciting weekend. Please read the honest cautions first.

Honest cautions first

Warning: A single spawn can produce hundreds of fry. A research colony recorded an average clutch of about 250 eggs (ranging from 12 to almost 500), and a Thai review notes a spawn can yield up to 500 fry. If even a fraction survive, you'll soon have dozens or hundreds of fish, and every male will eventually need his own tank or jar.

Time

Fry need feeding 2–4 times a day with live foods for weeks (the research colony feeds baby brine shrimp 2–4 times daily), plus frequent, careful water changes.
You'll need to hatch fresh baby brine shrimp every day and keep cultures (such as microworms) going before you spawn. The IBC beginner's guide warns that a couple of slip-ups with food could lose a whole tank of fry.
From spawning to the point where young males need separating is about 2–4 months, and fish need care for months after that until they're rehomed.

Space

A spawning tank, a grow-out tank (ideally more than one as fry grow), and then individual housing for every male from roughly 2–4 months old. The research colony starts housing fish individually from 8 weeks old; a Thai review notes young males may need isolating by about 4 months to stop fighting.

Cost

Extra tanks, heaters, sponge filters and air pumps, lids, water conditioner, test kits, brine shrimp eggs and hatchery equipment, live food cultures, many small containers for males, and electricity for heating them all.
Possible vet costs. Breeding pairs often tear fins, and young fish can get sick.
Bettas sell for very little. Most breeders lose money.

Culling and rehoming ethics

Not every fry will be healthy. Some will have deformities or illness. "Culling" means choosing which fish to keep, rehome or humanely euthanise.
The IBC guide describes culling "undesirables" between about 2 and 5 months. You need a plan for every fish before you start: who you'll rehome to, how you'll care for the ones you can't, and how you'll ensure any euthanasia is humane (ask an aquatic vet, and never use flushing, freezing or other methods that cause suffering).
A Thai review notes that on farms, females are usually sold cheaply. Think about where your females will go, too.
Never release bettas into the wild. It's illegal in many places, usually fatal for the fish, and can harm local wildlife (OATA).

Tip: If you love the idea of breeding but aren't sure, consider joining a betta club or the IBC first. Experienced breeders can mentor you, and you'll learn how much work (and joy) is involved before committing.

Conditioning

"Conditioning" means getting both fish in peak health before spawning.

Keep male and female in separate tanks, at about 80°F (26.7°C), the temperature the IBC guide says breeders agree on.
Feed a varied, high-quality diet including live or frozen foods (such as brine shrimp, daphnia or bloodworms) for 1–2 weeks, in small amounts several times a day, and keep up water changes. The research colony found that fish fed only dry food bred less successfully.
Watch for readiness:
- Male: building bubble nests, bright colour, flaring at the female.
- Female: a rounded belly, a visible white ovipositor (egg tube) behind the ventral fins, and vertical bars when she sees the male (OATA).
Let them see each other (side by side, through glass) for a while before spawning.

Pair selection

Healthy, mature, young adults. Both should be free of disease and have completed quarantine. The research colony notes that bettas can be mature as early as about 10 weeks, but it had no successful matings in fish older than about 40 weeks. Many breeders choose fish of a few months to under a year old.
Similar size. Avoid pairing a much larger male with a small female (or vice versa), as the bigger fish can injure the smaller.
Good temperament. An overly aggressive male may kill the female.
Type and colour. Choose fish of the same tail type and compatible colours for predictable results (see genetics below). The IBC guide recommends learning from experienced breeders.
Giants: pairing giants is a specialist area. Giant fry grow fast and need even more space and food, and giant males grow large enough that the size difference can be dangerous for a smaller female.

Genetics basics

Betta genetics are complex, and many traits are still not fully understood. Here's the basic idea, from the IBC guide and recent research:

Dominant and recessive genes

Each fish carries two copies of each gene, one from each parent. A dominant version shows even if there's only one copy; a recessive version shows only if the fish has two copies.

Example from the IBC guide: cross two fish that each carry one "red" and one "non-red" version (RY). Their offspring are expected to be:

Genes	Chance	Looks
RR	25%	Red
RY	50%	Red (carrying non-red)
YY	25%	Non-red

So about 75% look red and 25% don't. These are averages. A real spawn won't match exactly.

Colour layers

The IBC guide explains that betta colour comes from layers of pigment cells: yellow, red, black and iridescent (blue/green/steel). Different genes control how dense and widespread each layer is, which is how you get everything from pale "cellophane" to solid black.

Some quirks worth knowing

Melano (deep black) females are infertile. Breeders of black bettas usually pair a melano male with a female that carries the gene, such as a steel blue from a melano line (IBC).
Marble genes can make patterns change dramatically over the fish's life (IBC).
Koi, marble, candy and galaxy patterns are polygenic (controlled by many genes). A 2022 genome study mapped these "mosaic" patterns to nine regions on eight chromosomes. That's why koi bettas like Rip don't breed true and offspring can look very different from their parents.
Tail types have their own inheritance. Singletails, for example, can carry the doubletail trait (IBC).
Giants: a 2022 genome study found the giant trait is linked to specific genetic regions. Giants are about three times the size of wild-type bettas.

The breeding tank

Based on the IBC beginner's guide:

Item	Setup
Tank	About 5–10 gallons, with a cover. The IBC author uses the cover to stop drafts breaking up the nest.
Water depth	Shallow: 4–6 inches (10–15 cm), so the male doesn't have to swim far to rescue falling eggs and fry. A Thai review also suggests no more than 15 cm.
Temperature	80°F (26.7°C), steady
Water	Dechlorinated. Some breeders add Indian almond leaves (optional).
Filtration	None, or a very gentle sponge filter turned right down, since flow destroys nests.
Nest anchor	Something floating for the male to build under: half a foam cup, a plastic lid, or a floating leaf.
Female refuge	Floating plants or moss, and a glass lamp chimney (or a clear container) to keep the female safe while the male builds his nest.
Lighting	Normal room daylight is fine.

Spawning

The IBC guide gives a typical timeline:

Day	What happens
Day 1	Place the female in her clear chimney or container inside the breeding tank, and release the male into the open tank. He can see her but not reach her.
Day 2	Release the female once the male has a good nest (or the next morning). She can still shelter behind the chimney if he's rough.
Day 3 (usually)	Spawning. The male wraps around the female in an "embrace". Eggs fall, and the male collects them and places them in the nest. This repeats many times over hours. Afterwards remove the female promptly, because the male will chase her away.
Day 5	Fry hatch and hang from the nest. The male keeps returning any that fall.
Day 6	Remove the male in the evening, so a hungry male doesn't eat the fry.
Day 7	Start feeding the fry.

Tips and cautions

Some fin damage during spawning is common. The IBC author notes young fish usually regrow fins.
If there's no nest or spawn after about 4–5 days, the IBC author separates the pair and tries again a couple of weeks later.
Watch closely. If the female is being seriously injured, separate them immediately.
After spawning, give the female her own warm, clean tank, a quiet space and good food to recover, and watch torn fins for infection.

The male's care of the eggs

Male bettas are devoted fathers:

He keeps the nest topped up with new bubbles.
He collects eggs that fall and spits them back into the nest. The research colony found males retrieve about 90% of falling eggs.
The eggs stay in the nest for up to about 3 days. They hatch around 29–44 hours after fertilisation (research colony), at breeding temperatures.
He keeps returning fry that fall, until they're free-swimming (about 72 hours after fertilisation).
Leave him in peace. Don't feed him much, as he'll usually ignore food, don't change water, and keep the area quiet and dim.

Tip: Some males eat their first spawns, especially young or stressed males. It's frustrating but common. Make sure the tank is quiet, and try again after a rest.

Fry care, day by day

Times below are approximate and depend on temperature. Hours are counted from fertilisation (the spawn).

Age	What's happening	Your job
0–2 days	Eggs in the nest; hatching at around 29–44 hours	Leave the male to it; keep it quiet
2–3 days	Fry hang tail-down from the nest, living on their yolk sac. They become free-swimming at around 72 hours.	Get baby brine shrimp hatching 24 hours ahead; have microworms ready
3–4 days	Fry swim horizontally; remove the male (IBC Day 6)	Remove the male in the evening
4–5 days	Yolk runs out at around 120 hours (5 days)	Start feeding. The research colony found starting feeding at 5 days gave about 90% survival, versus about 75% when feeding started a day later. Feed small amounts 2–4 times a day.
First week of feeding	Tiny fry need tiny live food	The IBC guide uses newly hatched baby brine shrimp in the morning and evening, and microworms at midday, for the first 3 days, then baby brine shrimp twice daily. Remove dead brine shrimp and egg shells; the research colony warns shells cause gut blockages.
Week 1–2	A surface scum (protein film) can form	The IBC author adds a very gentle sponge filter at this point (about one bubble every 2 seconds).
Week 2–6	Growing fast. Labyrinth organ develops.	Small, careful water changes (see below); keep the air above the water warm with a lid; increase food as they grow.
About 6 weeks	Fry need more filtration	Turn the sponge filter up as much as fry can tolerate (IBC).
About 8 weeks	Some can be sexed; young males start building nests	Move to a larger grow-out tank; begin separating the largest fish and the males (research colony).
About 2 months	Fry ready for bigger live foods	The IBC guide moves fry to larger tanks and foods such as adult brine shrimp and worms.
2–5 months	Males become aggressive; individual personalities and quality show	Separate ("jar") males. Plan rehoming.

Warning: Keep a lid on the fry tank and the room warm. As the labyrinth organ develops (in the first weeks), cold air above the water is widely believed by breeders to harm fry. Keep the air above the water warm and humid.

Growth and water changes

Water changes are essential but delicate. Tiny fry are easily sucked up. The IBC author siphons through airline tubing into a glass jar so he can see and return any fry, and replaces water with conditioned water at the same temperature (80°F).
The IBC guide gives weekly water changes of a couple of gallons for fry up to 2 months old. As they grow and eat more, many breeders increase this. Test ammonia and nitrite regularly, as overfeeding fry fouls water fast.
Space: the research colony stocks juveniles at around 0.5–1 fish per litre in grow-out tanks. Crowded fry grow unevenly and the big ones may eat the small.
Temperature matters for sex ratio. The research colony notes that raising fry at cooler temperatures (23–25°C) may skew the spawn towards females. Keep fry at the same warm temperature as the spawning tank.
Feed to "rounded bellies": the IBC guide's rule of thumb is to check after 20 minutes. All fry should have round bellies with no food left over.

Jarring

"Jarring" means moving young males into individual containers so they don't fight.

Start when males begin sparring or nipping, usually from about 2–4 months, earlier for some lines.
Each male needs clean, warm water: individual containers in a heated room, or separate heated tanks. Small containers need very frequent water changes.
Put a sheet of card between containers so males can't see each other all day, removing it only for short periods.
Jars are a temporary stage on the way to a proper home. Long-term, every betta deserves the setup described in Tank setup.

Rehoming

Plan ahead: talk to local fish stores, betta clubs, friends and other hobbyists before you spawn.
Rehome fish only once they're healthy, eating well, and big enough to ship or travel.
Share care information with new owners. You could point them to this guide.
Be honest about any health issues.
Never rehome sick fish, and never release fish into the wild.
If shipping, use reputable methods and check local regulations.

Sources

Care guide by Betta Gillfriend (Bespok Labs, BC, Canada). It is general information, not vet advice. If your betta is sick, ask an aquatic vet.