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

Dario dario, the scarlet badis, is one of the smallest percoid fish known and a jewel of the nano-tank world. It belongs to the family Badidae and lives in clear, shallow, well-vegetated streams of the Brahmaputra tributary systems in the Indian states of Assam and West Bengal, possibly extending into Bhutan. Hamilton described it in 1822, and Kullander and Britz set up the genus Dario for it in their 2002 revision of the badids; the name comes from a local Bangla word for the fish. Males barely top 2 cm and females are smaller still, around 1.3 cm, and the sexual difference is extreme: males blaze with alternating scarlet and iridescent blue bars, while females are a plain grey, plain enough to look like another species. It is a micropredator, hunting tiny crustaceans, worms, insect larvae, and zooplankton. Most fish in the trade are wild-caught, though captive breeding is becoming more common, and its small, fragmented range has it listed as of conservation concern, with IUCN treating it as Data Deficient.

Breeding

Males court with spread fins and heightened colour, and a receptive female follows the male into his patch of plants or moss to spawn among fine leaves. Accounts of the details differ: most sources describe small clutches and little or no parental care, with the adults eating eggs and fry, though some report the male guarding the nest, so the picture is not settled. The eggs hatch in a couple of days, and the fry are tiny enough to need infusoria or paramecium at first before moving to vinegar eels and baby brine shrimp over a few weeks. In a thickly planted species tank a few young appear on their own, but growth is slow and rearing them is fiddly given the scale.

Common problems

Feeding is the make-or-break issue. Many scarlet badis flatly refuse dry and even frozen food and will only take live prey, so keeping them well means running cultures of baby brine shrimp, grindal worms, or daphnia, and a fish offered only flake can slowly starve amid plenty. Colour is the other thing to watch: a male with no rival males or females in view fades from scarlet to pale pink over weeks, so some social stimulation keeps him bright, while a male bullied into a corner in a small tank loses condition, which is why plenty of plant and hardscape sightline breaks help. Ich is uncommon in a settled tank, but any medication must be dosed lightly for so small a fish, and wild-caught stock can carry internal parasites that cause wasting.

Bioload

Further reading

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