Cardinal tetra care guide
Also called: Red neon tetra
The cardinal tetra is a small, peaceful schooling fish with an electric-blue stripe and a red band that runs the full length of its body. It looks like a larger neon tetra but prefers warmer, softer water and needs a group of 8 or more.
Cardinal tetras need a tank of at least 15 gallons (57 L), a group of 8 or more, and water at 23–28°C (73–82°F) with a pH of 4.5–7. They grow to about 4 cm (1.6 in) and are peaceful.
Plan a tank with cardinal tetrasSee all tank mates
Cardinal tetra quick facts
| Scientific name | Paracheirodon axelrodi |
|---|---|
| Family | Acestrorhamphidae |
| Origin | Upper Rio Negro and Orinoco basins in Brazil, Colombia and Venezuela (both wild-caught and farm-bred fish are sold) |
| Adult size | 4 cm (1.6 in) |
| Minimum tank | 15 gallons (57 L), at least 60 cm (24 in) long |
| Temperature | 23–28°C (73–82°F) |
| pH | 4.5–7 |
| Hardness (GH) | 1–8 dGH |
| Group size | 8 or more (schooling fish) |
| Temperament | Peaceful |
| Swims at | Middle |
| Diet | Omnivore |
| Care level | Moderate |
| Lifespan | 3–5 years |
| Safe with shrimp? | Mostly (eats baby shrimp) |
| Safe with plants? | Yes |
Tank setup
Give a group of 8–10 a tank of at least 15 gallons (57 L) and 24 in (60 cm) long; 20 gallons (76 L) or more is better. A planted layout with driftwood, leaf litter and shaded spots suits them best. Keep the current gentle and leave open water in the middle.
How many cardinal tetras in a tank?
The smallest common tank that suits cardinal tetras is a 15 gallon. Here is roughly how many fit in each size when they are the only fish, based on adult size and waste output. Leave room if you want tank mates.
| Tank | Cardinal tetras (alone) |
|---|---|
| 3 gallon | Too small |
| 5 gallon | Too small |
| 10 gallon | Too small |
| 15 gallon | 8–20 |
| 20 gallon | 8–27 |
| 20 gallon long | 8–27 |
| 29 gallon | 8–39 |
| 40 gallon | 8–54 |
| 55 gallon | 8–74 |
| 75 gallon | 8–102 |
| 125 gallon | 8–170 |
What you need for cardinal tetras
Sized for a 15 gallon tank, the smallest common size that suits a group of 8 cardinal tetras. For a different tank or a mix of fish, use the stocking calculator for a list sized to your plan.
Tank and equipment
- 15 gallon aquarium (tank or kit) (opens Amazon in a new tab)Bigger tanks are more stable and easier for beginners. How to choose
- Adjustable heater, 75 W (opens Amazon in a new tab)Holds about 78 °F (25.5 °C) in a room at 65 °F (18 °C). How to choose
- Aquarium thermometer (opens Amazon in a new tab)Check it daily: heaters can fail stuck on or off. How to choose
- Hang-on-back filter rated 60–90 GPH (opens Amazon in a new tab)Community tank: 4–6 times the tank volume per hour. How to choose
- About 35 lb of aquarium gravel (opens Amazon in a new tab)Enough for a layer about 2 in (5 cm) deep. Smooth gravel suits most community fish. How to choose
- Water conditioner (dechlorinator) (opens Amazon in a new tab)Removes chlorine and chloramine from tap water. Seachem Prime is a popular, concentrated choice. How to choose
- Liquid test kit (ammonia, nitrite, nitrate, pH) (opens Amazon in a new tab)Liquid kits are more accurate than strips. The API Freshwater Master Test Kit is the common choice. How to choose
- Gravel vacuum (siphon) (opens Amazon in a new tab)Cleans the gravel and does the water change in one go. How to choose
- LED aquarium light, about 24 in long (opens Amazon in a new tab)Match the light to the tank length. Basic LEDs grow easy plants. How to choose
Food and extras for cardinal tetras
- Micro pellets or flakes for small fish (opens Amazon in a new tab)Small enough for tetras, rasboras and other nano fish.
- Indian almond leaves (opens Amazon in a new tab)Release tannins that soft-water fish like bettas and rams enjoy.
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Water parameters
Keep them at 23–28 °C (73–82 °F) in soft, acidic to neutral water: pH 4.5–7.0 and 1–8 dGH. Wild-caught fish in particular do best in soft, slightly acidic water. Stable conditions matter more than exact numbers, so do not add them to a brand-new tank.
Best tank mates for cardinal tetras
These popular species share cardinal tetras' water needs and temperament. See the full list of 96 good matches.
Betta fish
6.5 cm (2.6 in) · 24–28°C (75–82°F)
Cherry shrimp
3 cm (1.2 in) · 20–27°C (68–81°F)
Nerite snail
2.5 cm (1 in) · 22–27°C (72–81°F)
Guppy
5 cm (2 in) · 22–27°C (72–81°F)
Dwarf gourami
7.5 cm (3 in) · 24–28°C (75–82°F)
Neon tetra
3.5 cm (1.4 in) · 21–25°C (70–77°F)
Panda corydoras
4.5 cm (1.8 in) · 21–25°C (70–77°F)
Bristlenose pleco
12 cm (4.7 in) · 22–26°C (72–79°F)
Avoid keeping cardinal tetras with
- Angelfish: Angelfish can eat cardinal tetras: they're small enough to fit in its mouth once it's grown.
- Common goldfish: They need different temperatures: Cardinal tetra 23–28°C (73–82°F), common goldfish 15–22°C (59–72°F).
- Oscar: Oscar can eat cardinal tetras: they're small enough to fit in its mouth once it's grown.
- Bala shark: Bala shark can eat cardinal tetras: they're small enough to fit in its mouth once it's grown.
- Chinese algae eater: Chinese algae eater is aggressive and will bully or injure peaceful cardinal tetras.
- Convict cichlid: Convict cichlid can eat cardinal tetras: they're small enough to fit in its mouth once it's grown.
Feeding
Cardinals are small omnivores that eat almost anything tiny enough to fit in their mouths. Offer a quality crushed flake or nano pellet every day, plus frozen or live daphnia, cyclops and baby brine shrimp. Two or three small meals a day suit them better than one large one.
Behavior
A peaceful mid-water schooler that shows its best color and behavior in a large group. It does not bother other fish or adult shrimp. Angelfish are a classic pairing, but adult angels often eat cardinals, so that mix is risky.
Breeding
Cardinals scatter eggs and are hard to breed at home. Use a small, dark spawning tank with very soft, acidic water (pH below 6, very low GH) at about 26–28 °C (79–82 °F), with fine plants or a spawning mop over mesh. Remove the adults as soon as eggs appear. The fry hatch in about a day and need infusoria first, then baby brine shrimp.
Tips from experienced keepers
- Wait until the tank is fully cycled and settled before adding cardinals. They cope with new-tank swings worse than neons.
- Keep at least 8. Larger schools are calmer and far more colorful.
- Indian almond (catappa) leaves and driftwood release tannins that tint the water and can lower pH a little, much like their blackwater home.
- They handle the warm water that discus and German blue rams need better than neon tetras do.
- Check for pale patches or sluggish fish before buying, and quarantine new arrivals.
Frequently asked questions
How many cardinal tetras should be kept together?
Keep at least 8, ideally 10 or more. In smaller groups they hide more and lose color.
Are cardinal tetras harder to keep than neon tetras?
Slightly. Their care is very similar, but cardinals prefer warmer, softer and more acidic water and are less forgiving of an immature or unstable tank.
Can cardinal tetras live with discus?
Often yes, because they cope with warm water better than most tetras. Keep the tank at the low end of the discus range, around 28 °C (82 °F), and add full-grown cardinals so they are not small enough to be eaten.
Sources
We checked these references when writing this page. Values are for healthy long-term keeping, not survival limits. Last reviewed 2026-10-13. See our editorial policy.