Scarlet badis

Quick facts

Adult size

2.5 cm

Lifespan

can live up to 4 years; small fish lifespan; 3-4 years typical with good care

Tank zone

all

Temperament

semi-aggressive

Difficulty

intermediate

Typically wild-caught

yes - acclimate slowly

Water parameters

Temperature

20–26°C

pH

6.5 to 7.5

Hardness

2 to 12 dGH

Tank requirements

Minimum volume

30 L

Minimum length

40 cm

Flow

low

Lighting

dim preferred

Substrate

any

Hiding spots

needed

Feeding

Diet: carnivore, feeds primarily at the all.

Extremely picky eater. Scarlet badis overwhelmingly prefer live food and many individuals refuse everything else entirely. Live baby brine shrimp, live daphnia, live grindal worms, and live microworms are the reliable staples. Frozen food (frozen baby brine shrimp, frozen daphnia, frozen cyclops) is accepted by some individuals but ignored by others. Dry food (flake, pellets) is almost always refused. This feeding requirement is the main reason scarlet badis aren't more popular: they need a consistent supply of live food, which is more effort than most hobbyists want to invest. Feed twice daily in small amounts. In tanks with shrimp, they'll supplement by hunting micro-crustaceans from the biofilm.

Live food required, will not accept dry or frozen alone.

Compatibility

• One of the smallest freshwater fish in the hobby at 1.5–2 cm. Males are vividly colored; females are tiny, drab, and rarely sold. Getting both sexes requires asking specifically or buying from a specialist.
• Not a community fish in the traditional sense. They're too small and too timid for standard community tanks. Best in a species tank or with very small, peaceful nano species: shrimp, snails, pygmy corys.
• Males are territorial toward each other and each defends a small area (about 15 cm radius). In a 40-liter tank, 2-3 males can coexist with enough visual barriers. In smaller tanks, one male only.
• Shrimp-safe with adults. The mouth is far too small to threaten even small Neocaridina. They'll eat newly hatched shrimplets if they find them, but the impact on a colony is negligible.

Habitat

Native to shallow, heavily vegetated streams and tributary pools in the Brahmaputra River drainage in India, particularly Assam and West Bengal. Found in slow-moving to still water with dense aquatic vegetation, leaf litter, and soft acidic water. The species (Dario dario) was described by Hamilton in 1822 but only entered the wider aquarium hobby in the early 2000s. Males are stunning: scarlet-red vertical bars alternating with iridescent blue-silver bars across a tiny body. Females are plain gray-brown with faint barring. The sexual dimorphism is extreme; males and females look like different species. Retailers often sell only males because females are harder to spot in collection and sell poorly due to their drab appearance. Without females, breeding is impossible, and keepers need to specifically request them. Adult size is among the smallest of any commonly kept fish: males reach about 2 cm, females about 1.5 cm. Wild-caught and tank-bred specimens are both available.

Breeding

Males display to females with spread fins and intensified color. If the female is receptive, she follows the male to his territory (usually among plant stems or moss) and the pair deposits eggs among fine-leaved plants. Clutch sizes are tiny (5-15 eggs per spawning event). Eggs are non-adhesive and fall into the plant mass. No parental care; adults eat eggs and fry when found. In a densely planted species tank, fry appear on their own over time. Dedicated breeding uses a small tank (10–20 L) with thick java moss, soft acidic water (pH 6.0-6.5), and a conditioned pair. Eggs hatch in 2-3 days. Fry are microscopic and need infusoria or paramecium for the first week. They graduate to vinegar eels, then baby brine shrimp nauplii over 2-3 weeks. Growth is very slow. Breeding is achievable but the tiny scale makes fry rearing demanding.

Common problems

Feeding is the defining challenge. Scarlet badis that refuse frozen and dry food need live food as the sole diet. Maintaining cultures of baby brine shrimp, grindal worms, or daphnia is the commitment. Without live food, some individuals starve despite food being available. Males without rival males or females lose color intensity over weeks, fading from vivid scarlet to pale pink. Social stimulation (visual contact with other males) maintains the display coloring. Aggression between males in small tanks can result in the subordinate being confined to a corner and losing condition. Provide sightline breaks with plants and hardscape. Ich is rare in established tanks but chemical treatments should be minimal given the tiny body mass. Internal parasites from wild-caught specimens cause wasting; treat with levamisole at very reduced dosage.

Bioload

Bioload coefficient: 0.3 (tiny carnivore with small protein-heavy diet; load similar to a chili rasbora).

Bioload coefficients are calibrated against the neon tetra as the anchor (1.0). See the methodology page for the formula and how each value was derived.

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size