Quick Stats
| Adult Size | 1.5–2 cm |
| Minimum Tank | 10 gal |
| Temperature | 22–26°C |
| pH Range | 6.0–7.5 |
| Hardness (GH) | 3–12 dGH |
| Difficulty | Medium |
| Temperament | Peaceful but shy (males territorial with each other) |
| Diet | Micro predator — live BBS, microworms, frozen bloodworm, Daphnia (often refuses dry food) |
| Schooling | 1 male + 2–3 females (or single male) |
Tank Setup
The Scarlet Badis (Dario dario) is a tiny jewel of a nano fish — adult males are bright scarlet with seven vertical stripes and electric blue highlights around the gills, and at 1.5–2 cm fully grown they are among the smallest fish in the hobby. They come from shallow, slow-moving, plant-choked streams in West Bengal, India, and they were introduced to the hobby in the early 2000s. A 10 gallon tank is the realistic minimum for a single male with 2–3 females, but a 20 gallon lets you keep multiple males (in a harem-style setup) and shows off their territorial display behaviour.
Maintain water parameters within: temperature 22–26°C, pH 6.0–7.5, hardness 3–12 dGH. They come from soft, slightly acidic water and they prefer it, but farm-raised fish tolerate a moderately broad range. They do not tolerate hard alkaline water well — push them into pH 8.0+ and GH 15+ and they fade, stop eating well, and shorten their lifespan. They also do not tolerate temperature extremes; the upper end of their range (26°C) is the upper end, not the target. I keep mine at 24°C and they thrive.
Set up the tank with dark sand or fine gravel, driftwood, dense planting (Java moss, Java fern, Anubias, Vallisneria), and floating plants like Salvinia or frogbit to dim the light. Scarlet Badis are shy by nature and need broken sight lines and dim lighting to feel secure — a bare-bottomed, brightly-lit tank will leave them pressed against the back glass for weeks. Provide visual boundaries — patches of Java moss, driftwood, plants — that break the tank into micro-territories, because males establish small territories and need to be able to claim one without seeing rival males across the tank. A gentle sponge filter is plenty.
Tank Mates
Scarlet Badis are peaceful but extremely shy, and they will not compete for food with anything faster or more aggressive than themselves. That combination rules out nearly every tetra, danio, and rasbora in the hobby — even Ember Tetras will out-eat a Scarlet Badis at every feeding. They do best either in a species-only tank or with other small, peaceful, slow-moving nano fish that share their preference for cool, dim, planted water.
Compatible tank mates include: Scarlet Badis females (mandatory if you keep a male), Celestial Pearl Danios (with caution — keep them in larger numbers so they don't bully the Badis at feeding), Pygmy Corydoras, Otocinclus, Cherry Shrimp, and small snails (Ramshorn, Malaysian Trumpet). Cherry Shrimp are an outstanding combo — the shrimp clean up after the Badis, and the Badis ignore adult shrimp (though they will eat shrimp fry). Avoid housing with anything fast (tetras, danios, rasboras), anything aggressive, anything with a mouth large enough to swallow a 2 cm fish, and anything that competes for tiny live foods (micro predators like Boraras species).
Males are territorial with each other and should not be kept together unless the tank is 20 gallons or larger with heavy visual barriers. The recommended stocking is one male with 2–3 females in a 10 gallon, or two males with 4–6 females in a 20 gallon long with plenty of plant cover. Two males in a 10 gallon will fight continuously; one male alone will pine and lose colour without female company. Buy them as a group if at all possible — adding new Scarlet Badis to an existing group is stressful and rarely works well.
Diet & Feeding
Scarlet Badis are micro predators. In the wild they eat tiny crustaceans, insect larvae, copepods, and other microscopic prey items among the vegetation. In the aquarium they need live and frozen foods — baby brine shrimp, microworms, vinegar eels, grindal worms, frozen bloodworm (chopped small), frozen Daphnia, and frozen cyclops. Their mouths are tiny even by nano-fish standards, and standard flakes and pellets are too large to swallow whole.
The single biggest problem keepers have with Scarlet Badis is getting them to accept dry food. Newly imported fish often refuse flakes and pellets entirely — they don't recognise them as food and will starve rather than eat them. The solution is patience: start with live baby brine shrimp and microworms exclusively for the first two weeks, then gradually introduce frozen Daphnia and frozen cyclops (which they usually accept because the movement in the current triggers their predatory response). Once they're eating frozen food reliably, you can try micro pellets (crush them small) and finely crushed flakes — but be prepared for some individuals to never accept dry food at all.
Feed small amounts twice daily, and feed only what they can eat in 5 minutes — uneaten live food will foul the water quickly. Scarlet Badis are slow, deliberate feeders that stalk individual prey items; they will not chase food across the tank. If you keep them with anything faster (including shrimp at feeding time), target-feed them with a turkey baster or pipette so the food lands directly in their territory. A flake-only diet will kill a Scarlet Badis within weeks; a varied live-and-frozen diet will keep them healthy, brightly coloured, and breeding for years.
Common Health Issues
The two biggest killers of Scarlet Badis are starvation and the stress of being added to a tank that isn't right for them. Newly imported Scarlet Badis come in starved, stressed, and prone to bacterial infections — they are caught wild, held in wholesale facilities with minimal feeding (often only frozen bloodworm, which is too large for them), and shipped to your local shop in a state that's already borderline. The first week in your tank is the critical period; if they survive the first month, they are usually fine long-term.
Like all aquarium fish, they are susceptible to ich when stressed, and they are unusually sensitive to copper and salt — which rules out the standard heat-and-salt ich treatment entirely. If ich breaks out in a Scarlet Badis tank, raise the temperature slowly to 26°C (1°C per day) and treat with a formalin/malachite green medication at half the label rate. Do not use salt. Do not use copper. Scarlet Badis will not tolerate either, and they are too small to absorb any dosing error. Avoid medications entirely if possible — clean water and stable parameters will resolve most issues without chemicals.
Prevention is straightforward: a planted, dim tank with stable water parameters, a varied live-and-frozen diet, no fast or aggressive tank mates, and quarantine new fish for two weeks before adding them. Scarlet Badis typically live 3–5 years in good conditions, with the upper end coming from tanks that have a steady supply of live food (a small Daphnia or microworm culture is the single best investment a Scarlet Badis keeper can make). The species is collected from the wild in limited numbers, so buy captive-bred fish if you can find them — they are hardier, already weaned onto processed food, and easier to keep.
Breeding
Scarlet Badis are egg-scatterers and breedable in a home aquarium, but they are a challenging project — far harder than danios or tetras, and harder even than Celestial Pearl Danios. Sexing is straightforward: males are bright scarlet with seven vertical stripes; females are much smaller, silvery-grey, and lack the red colour almost entirely. Condition a group with abundant live baby brine shrimp and microworms for two weeks, then move them to a 10 gallon spawning tank at 24°C, pH 6.5–7.0, with a spawning mop or dense Java moss.
Spawning happens in the early morning. A male displays to a female by flaring his fins and intensifying his red colour; if she accepts him they sidle together among the plants and scatter 10–30 tiny adhesive eggs. Scarlet Badis are not prolific — a single spawning event produces only a handful of eggs, and the male may eat them within hours if given the chance. Remove the adults after spawning or move the egg-laden Java moss to a separate hatching container.
Eggs hatch in 2–3 days at 24°C. The fry are extremely tiny — smaller than a grain of rice at hatch — and need microscopic first foods: infusoria, paramecia, or commercially-prepared liquid fry food for the first week, then graduate to vinegar eels or freshly-hatched microworms. Baby brine shrimp are too large for the first week. Scarlet Badis fry grow very slowly and are easily outcompeted by any other species in the tank — they need a dedicated grow-out tank with no other fish. This is a breeding project for an experienced keeper with an established live-food culture setup, not a beginner project.
Frequently Asked Questions
What size tank do Scarlet Badis need?
A 10 gallon is the realistic minimum for one male with 2–3 females. A 20 gallon long lets you keep two males with 4–6 females and shows off their territorial display behaviour. Anything smaller and the male has no space to claim a territory, and the females have no space to escape his attention.
Why won't my Scarlet Badis eat flake food?
Newly imported Scarlet Badis often refuse dry food entirely — they don't recognise flakes and pellets as food and will starve rather than eat them. Start with live baby brine shrimp and microworms for the first two weeks, then gradually introduce frozen Daphnia and frozen cyclops. Once they're eating frozen food reliably, try micro pellets and finely crushed flakes. Some individuals never accept dry food at all.
Can Scarlet Badis live with other fish?
Yes, but only with very specific tank mates. They are shy, slow, and easily outcompeted for food, so they need small, peaceful, slow-moving companions. Celestial Pearl Danios (in larger groups), Pygmy Corydoras, Otocinclus, and Cherry Shrimp are safe choices. Avoid anything fast or aggressive — even Ember Tetras will out-eat a Scarlet Badis at every feeding.
How can you tell male and female Scarlet Badis apart?
Males are bright scarlet with seven vertical stripes and electric blue highlights around the gills. Females are much smaller, silvery-grey, and lack the red colour almost entirely — they look like a different species. The size difference is dramatic: adult females are barely 1.5 cm, while adult males reach 2 cm. If you see a "bright scarlet Scarlet Badis" it is a male; if you see a "dull grey one", it is a female.