Can Betta (male) live with Cardinal tetra?

Temperature. Betta (male) does best at 24–30 °C (75–86 °F) and Cardinal tetra at 23–27 °C (73–81 °F). They share 24–27 °C.

Water. Their pH ranges overlap at 6–6.

Temperament and size. Betta (male) is semi-aggressive and grows to 7 cm; Cardinal tetra is peaceful and grows to 3.5 cm. Betta (male) swims at the top and Cardinal tetra at the mid, which spreads them out.

Tank size and groups. Plan on at least 20 US gallons, the larger of the two cautious minimums. Keep Cardinal tetra in a group of 8+. A starter mix of 1 Betta (male) and 8 Cardinal tetra in 20 gallons uses about 45% of the tank’s bioload capacity under our rules and grades A.

Keeping them together

• Feeding: both feed in open water. Feed small amounts two or three times a day so the slower eater gets its share.
• Aquascape: break up sight lines with plants, wood or rock, and give each fish its own hiding spots. Territorial fish settle faster when they can’t see each other all the time.
• Group size: a full group is not optional. A schooling fish kept in too small a group is stressed and more likely to nip or hide.
• Shrimp and snails: neither is a known invertebrate eater, but baby shrimp can still be eaten. Dense moss helps.
• Adding them: add the calmer species first and let it settle for a week or two before adding the other, and only once your tank has cycled.

Better matches for Betta (male)

These pass every rule with Betta (male): Bristlenose pleco · Bronze corydoras · Cherry barb · Dwarf gourami · Guppy · Harlequin rasbora · Honey gourami · Kuhli loach.

Open this pair in the checker Add your other fish to grade the whole tank.

Quick facts

Data from the Species Ledger, checked November 9, 2026, with at least two sources per species. Cautious community guidelines, not guarantees: individual fish vary. Not veterinary advice. Disagree? Tell us.