Best Live Food for Betta Fry — A Week-by-Week Feeding System

Most betta spawns are not lost to disease, bad genetics, or bad luck. They are lost in the first two weeks, at feeding time, because the fry were offered food they physically could not eat. A betta fry is roughly the size of an eyelash when it becomes free-swimming. Its mouth opens to a fraction of a millimetre. Drop a pinch of crushed flake into that tank and almost none of it gets eaten — but all of it rots, the ammonia climbs, and the fry die in a tank that looked, to the keeper, perfectly clean.

This guide is the feeding system that prevents that. It is built around one principle that decades of breeding practice and aquaculture research both confirm: for the first weeks of life, fish fry are triggered to eat by movement, and the food must be small enough to swallow whole. Get those two things right — live and tiny — and survival rates climb dramatically. Get them wrong and no amount of water changes will save the spawn.

Below is the exact week-by-week schedule, the foods that work at each stage, how much to feed, and the water-quality discipline that makes live feeding safe rather than dangerous. If you are raising your first spawn, read it in order. If you have raised fry before and just want the schedule, jump to the feeding timeline.

Why Betta Fry Cannot Eat Normal Food

A free-swimming betta fry is about 3–4 mm long. Its mouth gape — the widest food particle it can take — starts at well under half a millimetre. That single number drives every decision on this page. A food can be the most nutritious substance on earth, but if a particle is wider than the fry's mouth, it is not food. It is waste.

This is why the classic beginner mistakes fail so reliably:

• Crushed flake or pellet dust clumps the moment it hits water, and even the "dust" is usually too large. Fry ignore it; it decays.
• Hard-boiled egg yolk is a traditional first food, and fry will eat the finest particles — but it fouls water faster than almost anything else, and a single overfeed can crash a small fry tank in hours.
• Commercial "fry powder" is convenient and has a place later, but newly free-swimming fry largely cannot detect it. It does not move, so it does not trigger the feeding response, and most of it sinks uneaten.

There are two requirements a first food has to meet, and they are non-negotiable:

1. Small enough to fit the mouth. Sub-millimetre for the first week.
2. Alive and moving. Movement is what makes a fry strike. Live prey also stays alive in the water column instead of sinking and rotting, which buys you margin on water quality.

The core rule of fry feeding: if it does not move, a newly free-swimming fry probably will not eat it — and whatever they do not eat becomes ammonia. Live food is not a luxury here. For the first two weeks it is the difference between a spawn that grows and a spawn that disappears.

The Week-by-Week Feeding Timeline

Betta fry develop fast, and their mouths grow with them. The feeding plan is a staircase: you start with the smallest live foods and step up as the fry can handle larger prey. Here is the schedule that maps food to age.

A few things about this table matter more than the rest. Do not feed for the first two to three days after the fry become free-swimming if they still have a visible yolk sac — they are still living off it, and food added early just pollutes the water. You will know they are ready when they are swimming horizontally and hunting, not hanging at the surface. And notice that the foods overlap: you do not stop microworms the day you start brine shrimp. You layer them, because a mix of prey sizes means every fry — the runts and the front-runners — finds something it can eat.

The First Foods (Day 3–7)

This is the make-or-break window. The fry are at their smallest and most fragile, and the food has to be correspondingly tiny.

Infusoria and green water

Infusoria is a catch-all term for the microscopic organisms — protozoa, rotifers, and similar — that bloom in mature, biologically active water. "Green water" (a controlled bloom of single-celled algae) feeds those organisms and is itself grazed by the smallest fry. This is the most natural possible first food and it is essentially free if you culture it in advance. The catch is density: a thin infusoria culture will not sustain a large spawn, so it works best as a supplement alongside microworms rather than the sole food.

Microworms — the workhorse first food

If you only culture one fry food, culture microworms. Panagrellus redivivus is a tiny nematode, roughly 0.5–2 mm long and thin enough for day-old fry, that stays alive and wriggling in the water for 12–24 hours after you add it. That lifespan is the whole point: the worms keep moving and triggering strikes long after you have walked away, and uneaten worms do not immediately foul the water the way egg yolk or powder does.

Microworms outperform powdered foods on fry survival and growth for the simple reason that fry can both detect them and catch them. A microworm culture is cheap to maintain on oats or bread, produces continuously for weeks, and is the standard first food in serious betta and killifish breeding. Blackwater Aquatics sells a ready-to-harvest live microworm culture, and their step-by-step culturing guide walks through keeping it productive if you want a self-sustaining supply.

Practical tip: harvest microworms by wiping a clean finger or cotton swab up the side of the culture container where the worms climb, then swirl it into the fry tank. Feed a small amount two to three times a day. You want a light haze of moving worms, not a cloud.

Vinegar eels — the slow-release backup

Vinegar eels (Turbatrix aceti) are even smaller than microworms and, crucially, they swim in the water column for days rather than hours. That makes them an excellent insurance food for the smallest fry and for situations where you cannot feed often — they stay available between feedings. They are lower in total yield than microworms, so most breeders run them as a complement, not a replacement.

The Growth Engine: Baby Brine Shrimp (Week 1–8)

Around day seven to ten, the fry are big enough for the food that does more for growth than anything else on this list: freshly hatched baby brine shrimp, almost always abbreviated BBS (Artemia nauplii).

Newly hatched brine shrimp are about 0.4–0.5 mm, packed with yolk, and they swim with a jerky motion that betta fry find irresistible. Breeders consistently report that the day fry start taking BBS is the day growth visibly accelerates — and a well-fed fry that grows fast is a fry that out-competes disease and stress. The high lipid content is exactly what a rapidly developing fry needs.

The one demand BBS makes is that you hatch it fresh. Brine shrimp are most nutritious in the first several hours after hatching, while they still carry their yolk reserve; after that the food value drops. So serious fry-rearing runs a small hatchery on a rotation — a bottle or cone of salted water with an air line, hatching a new batch every day or two. Blackwater's guide to hatching baby brine shrimp covers the salt ratio, temperature, and harvest method.

A genuine head-to-head on the two foundational fry foods, since this is the most common question breeders have:

The short version: microworms get the fry started; baby brine shrimp grow them out. Use microworms from day three or four, layer in BBS around day seven to ten, and run both together through the first month so the smaller fry always have microworms while the larger ones gorge on shrimp. For the full breakdown, see Blackwater's comparison of microworms vs baby brine shrimp for fry.

Stepping Up: Daphnia and Scuds (Week 4 Onward)

As the fry become recognizable little bettas — by roughly week four to eight — their mouths can handle larger, meatier prey, and their diet should broaden.

Daphnia (water fleas) come in next. Adult daphnia are too big for young fry, but sieved or small daphnia are an excellent grow-out food, and they bring a bonus: the chitin acts as a gentle laxative that keeps developing digestive systems clear, which matters when fry have been gorging on rich brine shrimp. Daphnia also filter and clean the water they live in. A live daphnia culture gives you a renewable supply, and the daphnia culture guide covers keeping it from crashing.

Scuds (freshwater amphipods) are the food the juveniles graduate into, and they are arguably the best long-term conditioning food a growing betta can have. They are high-protein, they trigger the hunting behaviour that keeps a fish mentally engaged, they are self-cleaning — they will not die and foul the tank the way other foods can — and a culture can become a self-sustaining food source right in a grow-out tank. Small scuds suit larger juveniles; full-size scuds are for sub-adults and adults. This is the point where your grow-out fish start eating like the adults they are becoming. Blackwater's live scud culture is the same flagship food used to condition breeding adults, and why scuds beat pellets explains the color and conditioning benefits in depth.

The throughline from fry to adult: microworms → baby brine shrimp → daphnia → scuds. It is one continuous live-food staircase. Each step matches the growing mouth and the growing nutritional demand, and the fish never has to relearn how to hunt because it has been hunting live prey its whole life.

How Much, How Often

Underfeeding stunts fry; overfeeding kills them through fouled water. The target is small, frequent meals.

• Frequency: 3–5 small feedings a day for the first month. Fry have tiny stomachs and fast metabolisms; they do better with many small meals than one large one.
• Amount: feed only what the fry can clear in a few minutes. With live foods you have more leeway — living microworms and BBS persist rather than instantly rotting — but the discipline still holds.
• The belly check: healthy, well-fed fry develop visibly rounded, often orange-tinted bellies after a brine shrimp feeding. A tank of round-bellied fry is a tank that is feeding correctly. Flat, thin bellies mean the food is too big, too sparse, or not being detected.

A useful habit is to watch the first thirty seconds after you feed. If the fry dart and strike, the food is the right size and they are hungry. If they ignore it, the particle is probably too large or they are not yet free-swimming — stop and reassess rather than adding more.

The Real Killer: Water Quality

Here is the hard truth that catches new breeders: with fry, the food and the water-quality problem are the same problem. A fry tank is small, lightly filtered (a sponge filter on gentle air, so fry are not sucked in), and stocked with dozens or hundreds of animals. Every bit of uneaten food is concentrated ammonia in a system with very little buffering.

This is exactly why live food is safer than it sounds. Live microworms, vinegar eels, and brine shrimp stay alive and edible instead of decaying the instant they are ignored, which dramatically lowers the fouling risk compared to powders and egg yolk. But "safer" is not "safe": leftover brine shrimp die within hours in freshwater, and a heavy overfeed still spikes ammonia.

The disciplines that keep fry alive:

• Gentle, daily water changes. Small (10–20%), temperature-matched, dripped in slowly or added against the glass so the current does not batter the fry. Use the water change calculator to dial in volumes as the tank matures.
• Understand the cycle you are working inside. A fry tank's bioload climbs fast as they grow. If you are not confident on ammonia, nitrite, and nitrate, the nitrogen cycle tracker is worth running alongside the spawn.
• Siphon the bottom. Use airline tubing to spot-siphon dead brine shrimp and detritus off the bottom daily. This single habit prevents most fry-tank ammonia spikes.
• Do not over-clean. Fry graze on biofilm and infusoria growing on surfaces. A sterile tank is a tank with no backup food. Remove waste, not the living film.

For the betta-specific water parameters your fry are growing into — temperature, pH, hardness — see the betta fish care guide, which covers the adult targets you are raising them toward.

Common Fry-Feeding Mistakes

Almost every lost spawn traces back to one of these:

1. Feeding too early. Fry with a yolk sac do not need food, and early feeding only pollutes. Wait until they are free-swimming and hunting horizontally.
2. Food too big. The single most common killer. If the fry are not visibly eating, assume the particle is too large before you assume anything else.
3. Relying on powder alone. Powdered fry food has a role as a supplement later, but it is not a substitute for live food in the first two weeks.
4. Overfeeding rich foods. A heavy brine shrimp feed with no bottom siphon is how clean-looking tanks crash overnight.
5. One food, one size. Fry in a spawn grow at different rates. A single prey size leaves the smallest fry unable to compete. Layer sizes.
6. Skipping water changes to "avoid stressing" the fry. Stable, clean water is less stressful than accumulating ammonia. Gentle and frequent beats rare and large.

Setting Yourself Up Before the Spawn

The breeders with the best survival rates have one thing in common: their fry foods were cultured and producing before the eggs hatched. You cannot start a microworm culture the day the fry go free-swimming — it needs days to ramp up. The same is true of green water and a brine shrimp hatching rhythm.

A sensible pre-spawn checklist: start a microworm culture (and ideally a backup) one to two weeks ahead, get a green-water or infusoria culture going, and have your brine shrimp hatchery and eggs on hand. Keeping live cultures running continuously — even between spawns — means you are never caught feeding the wrong thing at the worst possible moment. Blackwater Aquatics ships live microworm, daphnia, and scud cultures across Canada, which is the simplest way to have all three stages on hand before you ever introduce the pair.

Frequently Asked Questions

What is the best first food for betta fry?

Microworms are the best practical first food for newly free-swimming betta fry. They are small enough for a day-old fry, they stay alive and moving in the water for 12–24 hours so they keep triggering feeding strikes, and they produce far better survival and growth than powdered foods. Many breeders run microworms alongside infusoria or green water for the first few days, then add baby brine shrimp around day seven to ten.

When do I start feeding betta fry?

Do not feed while the fry still have a visible yolk sac and are hanging at the surface — usually the first two to three days after hatching. Start feeding once they are free-swimming and hunting horizontally. Feeding earlier only pollutes the water, since they are still living off the yolk.

Can betta fry eat baby brine shrimp right away?

Not on day one. Newly free-swimming fry are usually a little too small for brine shrimp and do better starting on microworms or infusoria. Introduce baby brine shrimp around day seven to ten, once the fry have grown, and feed it freshly hatched for the highest nutritional value. From that point it becomes the main growth food.

Why is my betta fry food not being eaten?

The most common reason is that the food particle is too large for the fry's mouth, which opens to well under half a millimetre at first. The second most common is that the fry are not yet free-swimming and still feeding on their yolk sac. Switch to a live food sized for fry, such as microworms, and confirm the fry are actively swimming and hunting before increasing the amount.

How often should I feed betta fry?

Feed small amounts three to five times a day for the first month. Fry have tiny stomachs and fast metabolisms, so frequent small meals grow them faster and pollute less than one large feeding. Watch for rounded bellies after feeding as the sign you are feeding enough.

How do I keep a fry tank clean while feeding live food?

Spot-siphon the bottom daily with airline tubing to remove dead brine shrimp and detritus, and do small (10–20%), temperature-matched water changes added gently so the current does not batter the fry. Live foods foul the water far more slowly than powders, but leftover brine shrimp still die within hours in freshwater, so daily siphoning is the key habit.

What do betta fry eat as they grow up?

Follow the live-food staircase: microworms and infusoria first, then baby brine shrimp as the main growth food, then sieved daphnia, and finally small scuds and chopped frozen foods as juveniles. Each step matches the widening mouth and rising nutritional demand, and keeps the fish hunting live prey continuously from fry to adult.