Scarlet Badis Care Guide: The Micro Predator for Nano Tanks
The scarlet badis (Dario dario) is one of the most stunningly colourful freshwater fish you can keep — and one of the smallest. Males display an extraordinary pattern of alternating scarlet red and iridescent blue vertical bars that rivals any marine fish for sheer beauty. At just 1.5 to 2 centimetres, the scarlet badis is a true micro predator perfectly suited to nano aquariums. However, scarlet badis care presents unique challenges, particularly around feeding, that every prospective keeper should understand before bringing one home. This guide covers everything you need to succeed with this remarkable little fish.
Origin and Appearance
Scarlet badis are native to the tributaries and shallow streams of the Brahmaputra River basin in India, particularly in Assam and West Bengal. They inhabit clear, slow-moving waters with dense marginal vegetation, where they hunt tiny invertebrates among submerged plant roots and leaf litter.
The species belongs to the family Badidae, which are sometimes called chameleon fish for their ability to subtly shift colouration depending on mood and environment. Male scarlet badis are among the most vividly coloured freshwater fish in the world. Their bodies display seven or more vertical bars of intense scarlet red alternating with bands of shimmering blue, set against a pale background. The unpaired fins are edged in electric blue. When displaying to females or rival males, the colours intensify dramatically.
Fully grown males rarely exceed 2 centimetres in total length, making Dario dario one of the smallest known perciform fish. Their diminutive size is part of their appeal — a single scarlet badis can turn a modest 20-litre nano tank into a captivating display.
Male vs Female Identification
The difference between male and female scarlet badis is dramatic, and this disparity is worth understanding because it affects what you receive when purchasing them.
Males display the characteristic scarlet and blue banding that gives the species its common name. They are slimmer, slightly larger and far more colourful. Males are almost always what you see for sale in aquarium shops.
Females are considerably plainer — a uniform silvery-grey with faint, barely visible barring. They are also slightly smaller than males. Females are rarely imported or sold because they look unremarkable, and many shops do not stock them at all. If you want to breed scarlet badis, you may need to specifically request females from your local fish shop or online seller.
It is also worth noting that stressed or subordinate males can temporarily fade their colours, sometimes making them difficult to distinguish from females at first glance. A healthy, dominant male in good conditions will display vivid colouration almost constantly.
Tank Size and Setup
Scarlet badis are ideal candidates for nano aquariums. A single male can thrive in a well-maintained tank as small as 15 to 20 litres. For a pair or trio (one male and two females), 30 litres is suitable. If keeping multiple males, provide at least 30 litres per male with heavy planting and visual barriers to reduce territorial aggression.
The key to a successful scarlet badis tank is dense planting. In open, sparsely decorated tanks, scarlet badis become extremely shy, spending most of their time hidden and often refusing food. A well-planted environment gives them the confidence to come out, explore and hunt.
Recommended setup elements include:
- Dense stem plants — Hygrophila, Rotala and similar species create excellent cover
- Mosses — Java moss attached to hardscape provides hunting grounds where microfauna thrive
- Floating plants — these dim the lighting and help shy fish feel secure
- Fine-leaved plants — create a complex, layered environment
- Driftwood and small rocks — territorial markers and hiding spots
- Gentle filtration — a sponge filter is ideal; strong current stresses these tiny fish
A dark substrate and subdued lighting (or dappled light through floaters) bring out the best colouration in scarlet badis. Under harsh, bright lighting with nowhere to hide, they will appear washed out and stressed.
Water Parameters
| Parameter | Ideal Range | Notes |
|---|---|---|
| Temperature | 22 – 27 °C | Prefers slightly cooler; a fan may help in Singapore |
| pH | 6.5 – 7.5 | Neutral to slightly acidic preferred |
| GH (General Hardness) | 2 – 15 dGH | Adaptable to a range of hardness |
| KH (Carbonate Hardness) | 2 – 10 dKH | Moderate buffering capacity |
| Ammonia / Nitrite | 0 ppm | Very sensitive to poor water quality |
| Nitrate | Below 15 ppm | Keep low with regular water changes |
One consideration for Singapore keepers is that scarlet badis prefer the cooler end of tropical temperatures. Our ambient room temperatures of 28 to 32 degrees Celsius can be slightly higher than ideal. A small clip-on fan blowing across the water surface typically reduces temperature by 2 to 3 degrees, which brings conditions into a more comfortable range. Alternatively, keeping the tank in an air-conditioned room works well.
Feeding Challenges
Feeding is the most demanding aspect of scarlet badis care, and the reason many aquarists struggle with this species. Scarlet badis are micro predators with a strong instinct to hunt tiny moving prey. The majority of individuals will flatly refuse flakes, pellets and other dry foods, no matter how hungry they become. Some may eventually accept high-quality micro pellets, but you should never count on this.
Reliable food sources include:
- Live baby brine shrimp (BBS) — arguably the best staple food; easily hatched at home
- Frozen bloodworms — cut into small pieces, as full-sized bloodworms may be too large
- Live daphnia — eagerly accepted and nutritious
- Frozen cyclops — appropriately sized for their tiny mouths
- Grindal worms or micro worms — excellent live food cultures for dedicated keepers
- Vinegar eels — very small live food, useful as supplementary feeding
In a mature, well-planted tank with established biofilm and microfauna, scarlet badis will supplement their diet by hunting copepods, seed shrimp (ostracods) and other tiny organisms living among the moss and plant roots. This is one reason why a mature tank with dense planting is so important for this species — it provides a living pantry between scheduled feedings.
Feed small amounts once or twice daily. Watch carefully to ensure each fish is eating, as subordinate individuals may be bullied away from food by dominant males.
Behaviour and Temperament
Male scarlet badis are territorial, and while their territories are small (roughly 20 to 30 centimetres in diameter), they defend them vigorously against other males. Territorial disputes involve intense colour displays, flared fins and parallel swimming — genuine physical combat is rare but can occur in cramped quarters.
Despite their boldness towards conspecifics, scarlet badis are extremely shy around larger fish. In a community tank, they are easily outcompeted for food and may retreat permanently into hiding. This is why species-only tanks or very carefully chosen nano tank mates produce the best results.
Scarlet badis are diurnal hunters, spending their active hours patrolling their territory and picking off tiny invertebrates from plant surfaces. Watching a scarlet badis stalk and strike at a baby brine shrimp is genuinely fascinating — their predatory behaviour is deliberate and precise, more akin to a cichlid than a typical nano fish.
Tank Mates
Due to their tiny size, shyness and specialised feeding requirements, tank mate selection for scarlet badis is limited. The best approach is a species-only tank, but if you want companions, consider only very small, peaceful species that will not outcompete or intimidate them:
- Chili rasboras — similarly sized, peaceful and occupy different areas of the tank
- Pygmy corydoras — bottom-dwelling and too small to threaten badis
- Small shrimp — adult cherry shrimp generally coexist well, though very small shrimplets may occasionally be hunted
- Snails — nerite or small ramshorn snails are ignored
Avoid all medium to large fish, fast swimmers, boisterous species and anything that may eat the scarlet badis. Also avoid other territorial bottom-to-mid dwellers that could compete for the same space.
Breeding
Breeding scarlet badis is achievable in the home aquarium, though obtaining females is often the hardest part. Once you have a male-female pair, courtship is fascinating to observe. The male intensifies his colours and performs a shimmying display to entice the female into his territory.
Spawning typically occurs among fine-leaved plants or moss. The female deposits a small clutch of eggs (often just 10 to 20), and the male may loosely guard the territory. Eggs hatch in two to three days at around 25 degrees Celsius. The fry are extremely tiny — among the smallest of any commonly kept aquarium fish — and require infusoria, paramecium or freshly hatched vinegar eels as their first food. After a week or two, they can graduate to baby brine shrimp.
Fry survival rates improve dramatically in tanks with established biofilm and dense moss growth, as these harbour the microscopic organisms that fry feed on naturally.
Common Health Issues
The most common problem with scarlet badis is starvation due to feeding difficulties. A healthy scarlet badis should have a gently rounded belly after feeding. If you notice a concave belly or a visibly thin fish, it is not eating enough and you need to reassess your feeding strategy.
Other health concerns include:
- Internal parasites — wild-caught specimens may carry parasites; quarantine and preventive treatment with praziquantel is advisable
- Bacterial infections — usually linked to poor water quality or stress
- Fungal infections — can appear on fins if the fish is weakened
Maintaining excellent water quality and providing a varied diet of live and frozen foods are the best preventive measures.
Singapore-Specific Considerations
Scarlet badis are increasingly available in Singapore’s aquarium shops, though you may need to visit specialist stores or check online sellers for consistent stock. Females remain difficult to find locally.
Singapore’s warm ambient temperatures (28 to 32 degrees Celsius) sit at the upper end of this species’ comfort zone. A small aquarium fan is a worthwhile investment to bring the temperature down to 25 to 27 degrees, where scarlet badis are most active and colourful. In air-conditioned rooms (23 to 25 degrees Celsius), no additional cooling is needed.
PUB tap water parameters are generally suitable after treatment with a water conditioner to remove chloramine. If you find the pH a little high, adding Indian almond leaves or driftwood will naturally lower it while providing beneficial tannins.
Frequently Asked Questions
Can scarlet badis eat dry food?
Most scarlet badis refuse all dry foods, including flakes and micro pellets. While a few individuals may eventually learn to accept pellets, you should plan on providing live or frozen foods such as baby brine shrimp, daphnia and frozen bloodworms as their primary diet. Never purchase a scarlet badis assuming it will eat dry food.
How many scarlet badis can I keep together?
In a 30-litre tank, one male with one or two females is a good combination. If keeping multiple males, allow at least 30 litres per male and ensure dense planting to break sightlines between territories. In a 60-litre tank, two to three males with several females can coexist if the tank is well-structured.
Are scarlet badis aggressive?
Males are territorial towards other males of the same species, displaying and chasing to defend their patch. However, they are not aggressive towards other fish species — in fact, they are typically so shy that they are the ones being bullied or outcompeted. Aggression is only a concern when housing multiple males in too small a space.
Why is my scarlet badis hiding all the time?
Hiding is usually caused by insufficient plant cover, overly bright lighting, intimidating tank mates or the fish being newly introduced. Increase plant density (especially floating plants to diffuse light), remove any fish that may be bullying it and allow time for acclimation. A well-planted tank with gentle lighting encourages scarlet badis to explore confidently.
Interested in setting up a nano tank for scarlet badis or other micro species? Contact Gensou for expert advice and custom aquarium design. With over two decades of aquascaping experience, we specialise in creating beautifully planted tanks that bring out the best in even the smallest fish. Visit our shop at 5 Everton Park to see what is in stock.
Related Reading
emilynakatani
Still Have Questions About Your Tank?
Drop by Gensou Aquascaping — most walk-in questions get answered in under 10 minutes by someone who has set up hundreds of tanks.
5 Everton Park #01-34B, Singapore 080005 · Open daily 11am – 8pm
