Nano Fish Food Guide

Feeding nano fish is not the same as feeding big fish, and the difference is the mouth. A 4 cm chili rasbora has a mouth opening smaller than a pinhead — it cannot eat a standard flake without shredding it first, and it cannot eat a standard pellet at all. A 6 cm betta can eat a pellet, but only the right size, and the wrong food builds up in the gut and triggers swim bladder issues within a week. The same food that keeps a 15 cm angelfish thriving will literally starve a school of boraras to death over six months. This guide is the feeding system I use across my nano fishroom — what to feed, how much, how often, and what to never put in the tank.

Why Nano Fish Need Different Food

Mouth size is the obvious constraint, but the less obvious one is the fish's metabolic rate. Small fish have faster metabolisms relative to body mass than large fish — a chili rasbora burns through a meal in 6–8 hours, while an angelfish takes 24–36 hours. That means nano fish need more frequent, smaller feedings rather than one large daily meal. It also means they are more sensitive to a missed feeding — a 48-hour fast is fine for an adult angelfish, mildly stressful for a school of tetras, and dangerous for fry.

The second factor is water quality. A single overfeeding in a 10 gallon can spike ammonia from 0 to 0.5 ppm in 6 hours — enough to compromise gill function in sensitive nano species. The uneaten food decomposes, the biofilter cannot keep up, and the fish that survived the feeding die from the water quality crash that follows. Big tanks dilute the same overfeeding; small tanks concentrate it. Nano feeding is a water-quality discipline as much as a nutrition discipline.

The third factor is diet specialisation. Many nano species in the hobby are micro-predators — celestial pearl danios, chili rasboras, scarlet badis, ember tetras — evolved to eat tiny invertebrates and insect larvae from the water column. Their digestive systems are tuned for high-protein, low-carbohydrate food. Generic tropical flakes are 35% carbohydrate, which these fish cannot fully digest — the food passes through them, they get the calories but not the nutrition, and they slowly starve on a full stomach. The right food is not the same as the convenient food.

The 5 Food Categories

Nano fish food falls into five categories, and a healthy feeding rotation uses at least three of them. No single food is complete — even the "complete diet" pellets miss micronutrients that live and frozen foods provide. Below is the breakdown, with the use case for each.

Dry food is the daily staple — flakes and micro pellets form the backbone of the feeding rotation because they are cheap, convenient, and nutritionally complete if you buy the right brands. Flakes are the right choice for surface and mid-water feeders (tetras, rasboras, danios); micro pellets are the right choice for fish that eat in the water column or pick from the substrate (bettas, dwarf corydoras, badis). Wafers — algae wafers and bottom-feeder wafers — are the right choice for shrimp, otocinclus, and small plecos. Dry food keeps for 6 months unrefrigerated; after that the vitamins degrade and the food is just calories. Date your containers and replace every 6 months.

Frozen food is the variety and conditioning staple — bloodworms, brine shrimp, daphnia, and mysis shrimp, sold in foil blister packs at the fish store. Frozen food is nutritionally dense, fish love it, and it triggers breeding behaviour in conditioned pairs. The trap is overuse — bloodworms in particular are fatty, and feeding them daily causes fatty liver disease in fish within a year. Rotate frozen food 2–3 times a week in place of dry food, and never feed bloodworms more than once a week. Thaw frozen food in a cup of tank water before feeding — feeding it frozen shocks the fish's digestive system.

Live food is the gold standard for nutrition and the one most keepers skip because it is "too much work." Baby brine shrimp (BBS) hatched from cysts in 24 hours is the single best live food for nano fish — cheap, nutritionally perfect, and trigger-feeding response in even the fussiest eaters. Microworms (cultured on oatmeal in a tub) are the second-best — even easier than BBS, lasts weeks, perfect for fry. Infusoria (paramecium and similar micro-organisms, cultured in a jar with hay or banana peel) is the only food small enough for newly-hatched fry of egg-laying species. Live food is essential if you are breeding nano fish; convenient if you are not. The nano breeding guide covers live food culture in detail.

Vegetable food is for the herbivores and omnivores in the tank — shrimp, otocinclus, bristlenose plecos, and any fish that grazes on biofilm or algae. Blanched spinach (30 seconds in boiling water, then cooled in ice water) is the easiest — a 1 cm square per 5 shrimp, dropped in the tank and removed after 4 hours. Zucchini and cucumber slices (blanched or raw, weighted with a stainless steel spoon) work the same way. Vegetable matter keeps shrimp healthy, plecos from rasping on driftwood, and otocinclus from starving — otos often starve in new tanks because there is not enough biofilm, and supplemental feeding with blanched vegetables is the only reliable way to keep them alive.

Specialty food is the catch-all for the specific dietary needs that the other four categories do not cover. Algae wafers (Hikari Algae Wafers, Omega One Veggie Rounds) for bottom feeders and shrimp. Repashy gel food (Repashy Super Soil Green, Repashy Community Plus) for shrimp and bottom feeders — a powder you mix with boiling water, refrigerate, and cut into cubes; it stays intact in the tank for 12 hours without breaking down. Snail food (Micro Derp Mix, Snello recipes) for snail colonies. Specialty foods are daily staples for the species that need them; supplemental for everyone else.

Brand Recommendations

There are five brands I trust in my fishroom and a long list of brands I do not. The "trusted" list is short because the aquarium food market is full of cheap filler sold at premium prices, and reading the ingredient list is the only way to tell the difference. The first ingredient on the label should be a protein source (fish meal, krill, squid, shrimp) — not wheat flour, not soy meal, not "fish products." If the first three ingredients are plant-based, the food is filler with flavouring and you are paying for grain.

Hikari Micro Pellets ($8 for a 22g pack) are the default nano pellet. Three colour-coded pellets (red, green, yellow) in a tiny size that fits the mouths of fish down to 2 cm. The ingredient list leads with fish meal and krill — real protein, not filler. Fish love them, they float briefly then sink slowly so surface and mid-water feeders both get them, and they do not cloud the water. The 22g pack lasts a 10 gallon nano tank 4–6 months. The Hikari Micro Wafers are the same formula in a slightly larger flake form for bigger nano fish.

New Life Spectrum Nano ($12 for a 100g pack) is the upgrade pellet. Smaller pellet size than the Hikari (truly tiny, fits 2 cm fish easily), higher protein content (around 40%), and a broader ingredient list including krill, herring, squid, and seaweed. The colour-enhancing formula genuinely improves red and yellow colouration in fish like ember tetras and scarlet badis within a month. The 100g pack lasts a 10 gallon tank a year. Slightly more expensive than Hikari but worth it for the ingredient quality.

Repashy gel food ($12 for a 170g jar of powder) is the shrimp and bottom-feeder staple. You mix the powder with boiling water (3:1 powder to water by volume), stir into a paste, refrigerate until set, then cut into cubes or grate into the tank. Repashy Super Soil Green is the vegetable base for shrimp; Repashy Community Plus is the omnivore formula for community bottom feeders; Repashy Bottom Frenzy is the high-protein formula for loaches and catfish. A 170g jar makes months of food for a 10 gallon shrimp tank, and the gel stays intact in the tank for 12 hours without polluting the water.

Omega One flakes ($8 for a 28g can) are the flake staple. The first ingredient is whole salmon, whole krill, or whole herring — not "fish meal." The flakes are larger than the Hikari micro pellets but they break apart easily for smaller mouths. The Super Color flake variety enhances reds and yellows. Omega One also makes a Veggie Flake for herbivores and a Kelp Flake for additional vegetable matter. Rotate Omega One flakes with the Hikari pellets to vary the protein sources.

Feeding Schedule

The schedule I use across all my nano tanks is twice-daily feeding with one weekly fast day. Morning feeding is dry food (micro pellets or flakes); evening feeding is either more dry food or frozen food 2–3 times a week. The fast day is Sunday — the fish get nothing for 24 hours, which lets their digestive system clear out and prevents the fatty liver issues that come from constant feeding. This schedule has kept my nano tanks healthy for five years without a single food-related disease outbreak.

Shrimp tanks run a different schedule — every other day, a single small feeding. Shrimp do not need daily food in an established tank because they graze on biofilm, algae, and detritus between feedings. Overfeeding shrimp is the single most common way to crash a shrimp tank — uneaten food spikes ammonia, the shrimp die in 24 hours, and the keeper is left wondering what went wrong. Feed a piece of Repashy gel or a blanched spinach leaf the size of a pea, remove after 4 hours, and skip the next day. The shrimp will be healthier than if you fed daily.

Fry tanks run yet another schedule — 4–6 small feedings per day. Newly-hatched fry of egg-laying species need infusoria or commercial fry food every 2–3 hours from dawn to dusk for the first week. After the first week, they graduate to microworms or BBS 3–4 times a day. By week three, crushed flakes 3 times a day are sufficient. Fry feeding is a commitment — if you cannot feed 4 times a day, do not breed egg-laying nano fish. Livebearers are easier — the fry are large enough to eat crushed flakes from birth, 3 times a day is enough.

How Much to Feed: The 30-Second Rule

The 30-second rule is the only portion-size metric that matters: feed what the fish can eat in 30 seconds. Watch the tank for the full 30 seconds after feeding — if food is still floating at the 30-second mark, you fed too much. If the substrate has food on it at the 30-second mark, you fed too much. If the fish are still hunting the substrate 30 seconds after the food is gone, you can feed a little more next time. Err on the side of less; nano fish are designed to survive lean periods in the wild and a slightly hungry fish is healthier than an overfed one.

For a 10 gallon with 12 nano tetras, the 30-second rule translates to roughly 2–3 micro pellets per fish per feeding — a total of 25–35 pellets, scattered across the surface so everyone gets some. For a betta, 4–6 micro pellets or 3–4 bloodworms per feeding. For a school of 6 pygmy corydoras, 4–5 bottom-feeder wafers broken in half. For a 10 gallon shrimp tank, a 1 cm cube of Repashy gel. These are starting points — adjust based on the 30-second observation.

The other side of portion control is removing uneaten food. If you accidentally overfeed, net the uneaten food out within 5 minutes — do not leave it to decompose. A piece of bloodworm that sits on the substrate for 12 hours will spike ammonia measurably in a 10 gallon. A 25% water change after a noticeable overfeed is cheap insurance. The 30-second rule prevents the problem in the first place, but the cleanup is the backup plan.

Specialized Diets

Some nano species have dietary requirements that the general rotation does not meet. These are the four I get asked about most often, and the specific feeding protocol for each.

Dwarf puffers (pea puffers) need snails in their diet to wear down their beak — the beak grows continuously, and without snail shells to grind it down, the puffer eventually cannot close its mouth and starves. Feed pond snails or ramshorn snails 2–3 times a week, bloodworms or brine shrimp 2–3 times a week, and skip the dry food — most puffers refuse it. Keep a small snail breeding tank to supply the puffer. The puffer care sheet covers the snail breeding setup.

Otocinclus are obligate biofilm grazers — in the wild they eat algae and micro-organisms off surfaces, and they will starve in a clean tank with no algae. Supplemental feeding with blanched zucchini or cucumber (sliced, blanched for 30 seconds, weighted with a spoon) 2–3 times a week is mandatory. Algae wafers are a backup but otos prefer real vegetable matter. The first sign of a starving oto is a sunken belly — once you see the sunken belly, the fish has days to live, not weeks.

Scarlet badis (Dario dario) are micro-predators that almost always refuse dry food. They need live or frozen food — BBS, microworms, daphnia, bloodworms. A scarlet badis fed only flakes will slowly starve over 3–6 months. The reliable diet is BBS hatched daily, supplemented with frozen daphnia and live microworms. If you cannot commit to daily live food, do not keep scarlet badis. They are rewarding fish but they are not for keepers who want to feed flakes.

Crystal red shrimp (and other Caridina shrimp) need biofilm more than they need commercial food. In an established planted tank with driftwood and dead leaves, the biofilm is the staple and commercial food is supplemental. Add a piece of Indian almond leaf or cholla wood to the tank — the biofilm that grows on it is the shrimp's natural food. Feed a tiny piece of Repashy gel or a specialised CRS food (BorneoWild, Shirakura) every other day, and remove uneaten food after 4 hours. The nano shrimp hub covers the full shrimp feeding protocol.

Foods to Avoid

Goldfish flakes for tropical fish. Already covered in the FAQ. Goldfish food is higher carbohydrate and lower protein than tropical food — feeding it to tropical nano fish causes fatty liver disease and faded colour within months. The few dollars you save buying goldfish food will cost you the fish within a year.

Freeze-dried food as a staple. Freeze-dried bloodworms, tubifex, and krill are convenient and shelf-stable, but they are nutritionally degraded compared to frozen or live — the freeze-drying process destroys vitamins and denatures proteins. Use them as an occasional treat (once every 2 weeks), not as a daily food. The other risk is bloating — freeze-dried food expands in the fish's stomach and can cause swim bladder issues. Pre-soak freeze-dried food in tank water for 5 minutes before feeding to rehydrate it.

Beefheart. Beefheart is a discus breeder's staple that has bled into the wider hobby. It is far too rich for nano fish — the fat content causes digestive issues and pollutes the water faster than any other food. Stick to aquatic protein sources (fish, krill, shrimp, squid) that match what the fish evolved to eat. A nano fish fed beefheart will not die immediately, but it will be dead within 6 months of a beefheart-heavy diet.

Bread, biscuit crumbs, rice, pasta. This should not need to be said, but people do it. Fish cannot digest cooked carbohydrates from human food. The food passes through them, they absorb nothing, and the tank pollutes. Do not feed your fish anything from your kitchen except the blanched vegetables listed earlier in this guide.

Wild-caught live food (from ponds and streams). Live daphnia, bloodworms, or tubifex collected from local ponds can carry parasites, bacteria, and pollutants that will wipe out a nano tank. Cultured live food (BBS from cysts, microworms from a starter culture) is safe. Wild-caught is not. If you want to collect live food, set up a culture tank at home and grow your own — the breeding guide covers the setup.

DIY Foods: Repashy and Vegetable Prep

The two DIY food categories worth the effort are Repashy gel recipes and vegetable prep. Repashy gel is the most cost-effective shrimp and bottom-feeder food in the hobby — a $12 jar of powder makes months of food, the ingredient list is clean, and you can customise the recipe by adding ingredients. The basic recipe is 3 parts powder to 1 part boiling water by volume, stirred until smooth, then refrigerated in a flat container until set (about 2 hours). Cut into cubes and freeze what you will not use in 2 weeks; refrigerated gel lasts 2 weeks, frozen lasts 6 months.

For vegetable prep, the four vegetables I keep on rotation are spinach, zucchini, cucumber, and broccoli. Spinach: blanch a single leaf in boiling water for 30 seconds, plunge in ice water to stop the cooking, cut into 1 cm squares, and feed one square per 5 shrimp. Zucchini: slice into 5 mm rounds, blanch 60 seconds, feed one round per 10 shrimp or per pleco. Cucumber: slice, weight with a stainless steel spoon, drop in raw — shrimp and plecos both love it. Broccoli: blanch a small floret for 90 seconds, feed whole — shrimp swarm it within an hour. Remove any uneaten vegetable after 4 hours; after that it starts to break down and pollute the tank.

The other DIY food worth knowing is snello — a gelatin-based snail food made from fish food, calcium carbonate, and gelatin, mixed and set in the fridge. Snello keeps snail colonies healthy and feeds the snails you are breeding as puffer food. The recipe is variable; search "snello recipe aquarium" and pick one that fits your ingredient list. A 30-minute prep session makes 3 months of snail food for under $5.

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