Quick answer: The scarlet badis (Dario dario) is a jewel of a nano fish, a tiny, fiery red-and-blue micropredator and one of the smallest fish in the hobby. It makes a stunning centerpiece for a small planted tank, but it comes with real catches. It usually refuses dry food and can quietly starve, so it needs small live or frozen foods. It is shy and easily out-competed, so it does best in a species-only tank or with almost nothing else. And stores sell almost only bright males, which are territorial with one another. Give one a heavily planted tank, small meaty foods, and peaceful or no tankmates, and it rewards you with incredible color.
Scarlet badis at a glance
| Detail | Scarlet badis |
|---|---|
| Scientific name | Dario dario |
| Also called | Scarlet gem badis, rainbow badis |
| Adult size | Males about 0.8 inch, females about 0.5 inch |
| Lifespan | Around 3 to 5 years |
| Temperature | 71 to 79 F (22 to 26 C) |
| pH | 6.5 to 7.5, soft to neutral |
| Minimum tank | 10 gallons, 20 for a harem or group |
| Temperament | Peaceful, but males are territorial |
| Diet | Micropredator, small live and frozen foods |
| Care level | Moderate, feeding is the challenge |
The feeding problem: why scarlet badis starve
If you take one thing from this guide, make it this. The most common way people lose a scarlet badis is starvation, and it happens quietly.
Scarlet badis are micropredators. In the wild they pick tiny live creatures out of the water and off plants, and in a tank they usually refuse dry flake and pellet food entirely. Offer them the wrong diet and they will slowly stop eating and waste away, often without any obvious sign until it is too late.
So feed them what they actually want: small live and frozen foods. Good options are frozen cyclops, daphnia, and baby brine shrimp (Artemia), plus tiny live foods like micro worms, grindal worms, and vinegar eels. Two honest details most guides skip:
- Avoid bloodworms and tubifex. They are too large and hard to digest for such a tiny fish and are best left out.
- They are slow, shy feeders. In a tank with faster fish, a scarlet badis simply does not get to the food in time. This is a huge reason they do best alone, and why feeding has to be aimed to actually reach them.
Some individuals will eventually accept frozen or even dry food, but never count on it. Plan to keep small meaty foods on hand from day one.
What scarlet badis look like, and males versus females
Scarlet badis are astonishingly small. Males reach about 0.8 inch and females barely half an inch, which makes them one of the smallest fish you can keep. A colored-up male is unmistakable, glowing scarlet red with electric blue vertical bars, while females are small and plain.
That difference matters when you buy, because of a quirk of the trade.
| Male | Female | |
|---|---|---|
| Color | Bright scarlet red with electric blue vertical bars | Small and plain grey, sometimes faint color |
| Size | Larger, up to about 0.8 inch | Smaller, around 0.5 inch |
| In stores | Almost all that shops sell | Hard to find |
Because only the males are colorful, shops overwhelmingly stock males and rarely sell females. That is worth knowing before you plan a group, since males are territorial with each other.
Setting up the tank
Scarlet badis come from slow, clear, heavily planted Indian streams, and the tank that copies that turns a shy, hiding fish into a bold, glowing one.
- A planted nano tank. Ten gallons is plenty for a single male or a small setup, and a 20 gallon fish tank gives room for a harem or a species group.
- Dense planting and lots of cover. Heavy planting, java moss, leaf litter, driftwood, and small caves and crevices give them the territories and hiding spots they need to feel secure. Our low light aquarium plants and fish tank decorations guides cover good options.
- Gentle flow. A sponge filter or a softly baffled filter suits them, since they dislike strong current.
- Subdued light. Like many shy fish, they color up best in a calmer, dimmer, well-planted tank rather than a bright, open one.
Water parameters
Keep the temperature between 71 and 79 F, the pH between 6.5 and 7.5, and the water soft to moderately soft. They are not especially fussy about exact numbers, but they do need clean, stable water, so keep ammonia and nitrite at zero and stay on top of small, regular water changes. A small fish in a small tank feels a swing quickly.
Group size, temperament, and aggression
Scarlet badis are mostly peaceful and loosely social, but the males are the catch. Each male stakes out a small territory and will spar with rival males, flaring and chasing to defend it and to show off.
There are two sensible ways to handle that. The best is a harem: one male with two or three females, so the male spreads his attention and no single fish is hounded, though this depends on finding females, which is not easy. If you can only get males, give each one space, roughly one male per 10 gallons, and break up sight lines with heavy planting and hardscape so they are not constantly in each other’s faces.
Tank mates
Here is the honest answer: scarlet badis do best in a species-only tank. They are so tiny, so shy, and such slow feeders that almost any other fish stresses them or out-competes them for food.
If you do want company, the one fish that reliably works alongside them is the galaxy rasbora, also called the celestial pearl danio. It shares their love of cool, planted, gentle water and is peaceful and small enough not to bully or out-eat them. Larger shrimp such as Amano shrimp can also work, though a scarlet badis will happily eat baby dwarf shrimp and other tiny invertebrates that fit in its mouth.
Avoid fast, boisterous fish and any active feeder that will strip the food before your slow badis gets a bite.
Breeding scarlet badis
Scarlet badis are rewarding to breed in a quiet, well-planted tank. A male sets up a small territory around a cavity, a leaf curl, a clump of moss, or a narrow crevice, and courts a female into it. After spawning he guards the eggs until they hatch, usually in about two to three days, and then loses interest in the fry. The fry are minute, so they need the smallest first foods like infusoria, rotifers, or vinegar eels before they can take baby brine shrimp. Clean, slightly acidic water and plenty of moss give the best odds.
Common scarlet badis problems
- A fish that has stopped eating. The classic and most dangerous problem. Almost always the wrong diet or being out-competed. Offer small live and frozen foods and make sure they reach the fish.
- Dull color and constant hiding. Usually a bare or bright tank, or stressful tankmates. Add planting and cover, and reconsider its company.
- Males fighting. A group of males in too little space with too few hiding spots. Give more room, more cover, or set up a harem with females.
- Wasting away in a community tank. Faster fish are eating everything first. Move the badis to a species tank or target-feed carefully.
FAQ
What do scarlet badis eat?
Small live and frozen foods. They are micropredators that usually refuse dry flake and pellets, so feed frozen cyclops, daphnia, and baby brine shrimp, plus tiny live foods like micro worms. Avoid bloodworms and tubifex, which are too big for them.
Do scarlet badis need live food?
Mostly, yes. Some individuals eventually take frozen or even dry food, but you should plan on small live and frozen foods to keep them healthy, because many will simply refuse dry food and slowly starve.
What size tank does a scarlet badis need?
Ten gallons is enough for a single male or a small setup, since they are true nano fish. A 20 gallon is better for a harem or a species group and stays more stable.
Can scarlet badis live with other fish?
They do best in a species-only tank. The one fish that reliably works with them is the galaxy rasbora. Larger shrimp can work too, though the badis will eat baby shrimp. Avoid anything fast or boisterous.
Are scarlet badis aggressive?
Only the males, and mostly toward each other. They spar over small territories. Keep a harem of one male with a few females, or give lone males space and cover, to keep the peace. They are not aggressive toward other calm species.
Why do scarlet badis stop eating?
Usually because they are being offered dry food they will not take, or being out-competed by faster tankmates. Feed small live and frozen foods, and keep them in a species tank or with very peaceful company so they can actually eat.
