Scarlet badis

Water parameters

Tolerated range for this species. Aim for the middle of each band rather than the extremes.

Tank and habitat

Substrate: any.

Behavior

Plant interaction: plant safe.

Typically wild-caught; acclimate slowly.

Feeding

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.

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.

Origin and habitat

Distribution appears restricted to tributary systems draining into the Brahmaputra River in West Bengal and Assam, India, though it may also range into Bhutan. The neotype locality is the Janali River, Raimana, Kokrajhar District, Assam. Collection for the trade is primarily from tributaries of the Teesta River in North Bengal. IUCN Data Deficient. Described by Hamilton in 1822; the genus Dario was erected by Kullander and Britz in 2002. The genus name derives from the Bangla name Darhi. Typically inhabits shallow, clear-water streams with sand or gravel substrates and dense marginal or aquatic vegetation. One of the smallest known percoid fish species: males usually do not exceed 2 cm, females around 1.3 cm. Males display vivid scarlet-red vertical bars alternating with iridescent blue bars; females are much plainer, with subdued coloration. The sexual dimorphism is extreme enough that the sexes can look like different species. A micropredator feeding on small aquatic crustaceans, worms, insect larvae, and zooplankton. Most trade specimens appear to be wild-caught; standardized captive breeding has not been widely established, and there is an identified need to develop breeding technology for the species. Lifespan roughly 3-6 years with good care. Males are territorial and do best in species-only nano setups or with very small, peaceful tankmates.

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

Further reading

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