Scarlet Badis (Dario dario)

Meet the Scarlet Badis, a tiny red micro-predator from India

The Scarlet Badis, Dario dario, is one of the smallest perch-like fishes in the hobby. It belongs to the family Badidae and comes from shallow, clear streams in the Brahmaputra drainage of West Bengal and Assam in India, and possibly Bhutan. Seriously Fish gives a maximum of 20 mm standard length (body without the tail), which places it among the smallest percoid fishes known.

Mature males are bright red with seven iridescent blue vertical bars on the flanks and grow extended dorsal, anal and pelvic fins. Females are smaller and plainer. It moves slowly, hunts tiny live foods with great care and suits a densely planted nano or species aquarium rather than a busy community tank.

Know its names and relatives

Seriously Fish notes that the seven blue bars of the male are unique within Dario, which helps tell this species from its close relatives. Its larger cousins in the genus Badis have their own badis category on our site.

Know what one purchase supplies

One purchase quantity supplies one live Scarlet Badis. The sex is not specified. Our photographs show a male; females are smaller, have no red or blue on the flanks and show indistinct bars or none. Seriously Fish notes that the species is easy to sex but that often only males are traded.

Size up the adult

• Adult length: about 2 cm standard length according to Seriously Fish. FishBase lists 1.5 cm for males and 1.2 cm for females, and Aquarium Glaser describes adults as 2–3 cm long, probably including the tail.
• Colour: males show their full red and long fins as they mature; young fish are often paler.
• Grouping: plan one male per small tank, with or without females, as explained below.

Have the tank planted and matured before you order, and read our delivery and live arrival information.

Plan a small aquarium the right way

Seriously Fish gives a minimum base of 45 × 30 cm, about 41 litres, for a pair or for one male with several females. That is a modest tank, but the fish's needs are specific: dense planting, territories for males, stable water and a reliable supply of tiny live or frozen food.

Run a three-point space check

1. Measure the base: at least 45 × 30 cm for a pair or a male with females.
2. Count the males: one male per tank of this size; more males need a larger, heavily planted tank so each can hold a territory.
3. Check the menu: make sure you can supply small live or frozen foods every day before buying.

Mature the filter first. The RSPCA explains that cycling takes at least two weeks, and fish should only be added once ammonia and nitrite have risen and fallen back to zero. Small tanks swing faster than large ones, so stability matters even more here.

Plant densely and spread out the shelters

In the wild the Scarlet Badis lives among dense vegetation. Seriously Fish lists Hygrophila, Limnophila, Ottelia, Rotala and Vallisneria at one locality, over sand or gravel. FishBase describes a collection stream 2–5 m wide and 30–70 cm deep, with clear water and dense plants over sand and fine gravel.

Give every feature a job

Our live plants guide for beginners covers easy plants that suit a tank like this. A mature, well-planted tank can also support tiny creatures for it to hunt between meals.

Match water values for the Scarlet Badis

This is an adaptable fish when it comes to chemistry, but it dislikes sudden change. Seriously Fish gives 18–26°C, pH 6.5–8.5 and 1–15 dGH. Aquarium Glaser gives a wider 16–28°C and says that any tap water safe to drink is suitable. FishBase notes about 26°C in the collection stream.

Read the sources side by side

We follow Seriously Fish because it sits inside the other sources. Keep ammonia and nitrite at zero and nitrate low, test weekly, and compare your tap water using our water matcher. Our water chemistry guide explains the readings.

Filter gently and keep the water clean

Seriously Fish uses a filter turnover of four to five times the tank volume per hour; for a 41-litre tank that is roughly 165–205 litres per hour. Aquarium Glaser describes the natural habitat as clear, moderately flowing water. Spread the flow with a spray bar or sponge so this small, slow fish is never pushed around.

Follow a weekly maintenance routine

1. Test ammonia, nitrite and nitrate before you start.
2. Change part of the water every week; the RSPCA recommends weekly changes of around 30% in its filtration advice.
3. Remove uneaten frozen food the same day, because it fouls a small tank quickly.
4. Treat new water with a dechlorinator and match its temperature.
5. Rinse sponges in removed tank water, never under the tap.

Live foods such as daphnia survive in the tank until eaten, which makes them cleaner to use than frozen foods in a small aquarium.

Feed small live and frozen foods every day

The Scarlet Badis is a micropredator. Seriously Fish describes a natural diet of small aquatic crustaceans, worms, insect larvae and zooplankton, and lists suitable foods as Artemia nauplii, Daphnia, grindal worm, microworm and banana worm. Aquarium Glaser says it does not eat dry food, takes frozen food readily and strongly prefers live food.

Build a measured week of meals

Feed small amounts once or twice a day and watch the fish eat. It feeds slowly and carefully, so faster tank mates can take everything before it gets a share. If it is not eating, offer live food first; Aquarium Glaser notes that it strongly prefers live food.

Introduce it calmly and watch the first week

Switch the lights off, float the sealed bag to equalise temperature, then add tank water gradually before releasing the fish and discarding the bag water. The RSPCA suggests floating the bag for half an hour and keeping the lights off for the rest of the day. Our guide on acclimatising new fish covers each step.

Use a first-week checkpoint plan

A new Scarlet Badis often hides for a few days and shows little colour. It usually colours up once it has claimed a territory and is eating well.

Watch condition and feeding closely

With a fish this small, feeding is the main health measure. A healthy Scarlet Badis has a gently rounded belly, clear eyes and fins held open, and it hovers and inspects the plants for food.

Match each sign to a first action

Avoid frequent bloodworm feeds even if the fish takes them eagerly; Seriously Fish links them to obesity and disease in this species.

Manage males and choose calm company

Seriously Fish describes the Scarlet Badis as slow-moving and retiring, easily intimidated or outcompeted for food by larger or more aggressive fish. It recommends keeping it alone or with small pelagic, open-water species. Rival males are aggressive to each other, especially in small tanks, so a small tank should hold one pair or one male with several females.

Screen companions with this table

Sources disagree on groups. Aquarium Glaser reports that groups of 10–20 interact without seriously harming one another, while Seriously Fish advises a group only in a larger tank where each male can hold its own territory. Start with one male unless you have a large, densely planted tank. Our tank mates tool checks temperature and pH overlap before you mix species.

For related fish, compare the larger Dwarf Chameleon Badis and the Chameleon Fish (Badis badis), or browse our loaches and oddball fish, the other fish category and our nano tank fish. Our article on small tropical fish covers more species for small aquariums.

Understand breeding behaviour

Seriously Fish describes the Scarlet Badis as a substrate spawner that forms temporary pair bonds. Courtship can last several days, and the spawning embrace itself takes only seconds. Eggs are scattered on the underside of a leaf or another solid surface; the female is then driven away and the male guards the territory.

Raise the fry

• Seriously Fish gives an incubation of 2–3 days; fry may take up to a week to absorb the yolk sac.
• First foods are infusoria-grade, then microworm and Artemia nauplii.
• Remove the eggs or the adults, because the adults prey on the fry once they hatch.
• Aquarium Glaser notes that, unlike other badis, it does not practise brood care, and that young occasionally appear on their own in densely planted tanks fed live food.

FishBase lists the species as Data Deficient on the IUCN Red List, so buying aquarium stock carefully and never releasing fish matters.

Answer Scarlet Badis buying questions

How big does the Scarlet Badis get?

About 2 cm standard length (body without the tail), according to Seriously Fish. FishBase lists 1.5 cm for males and 1.2 cm for females.

What should I feed a Scarlet Badis?

Small live or frozen foods such as Artemia nauplii, daphnia, grindal worm and microworm. Aquarium Glaser says it does not eat dry food, and Seriously Fish advises avoiding bloodworm and Tubifex.

Can I keep two males together?

Only in a larger, densely planted aquarium where each male can hold its own territory. In a 45 × 30 cm tank, keep one male, alone or with several females.

What size tank does it need?

Seriously Fish gives a minimum base of 45 × 30 cm, about 41 litres, for a pair or one male with several females, densely planted.

What water does it need?

Seriously Fish gives 18–26°C, pH 6.5–8.5 and 1–15 dGH. Aquarium Glaser says any drinkable tap water is suitable. Stability matters more than an exact number.

Is it a good community fish?

Not for a busy community. It is shy and slow to feed, so keep it alone or with small, calm open-water fish that cannot outcompete it for food.

Will I receive a male or a female?

The sex is not specified. Our photographs show a male; Seriously Fish notes that the species is easy to sex and that often only males are traded.

Will it eat shrimp?

Seriously Fish lists small aquatic crustaceans in its natural diet, so newborn shrimp are likely prey. Keep a shrimp breeding colony in its own tank.

Consult the care references

• Seriously Fish: Dario dario — taxonomy, distribution, habitat, footprint, water values, diet, behaviour, sexing and reproduction.
• FishBase: Dario dario — lengths by sex, collection habitat, common names and IUCN status.
• Aquarium Glaser: Dario dario — habitat, size, feeding, group behaviour, water and temperature.
• RSPCA: aquarium environment — filter cycling, water changes and introducing new fish.