Can Cardinal tetra live with Molly?

Temperature. Cardinal tetra does best at 23–27 °C (73–81 °F) and Molly at 21–28 °C (70–82 °F). They share 23–27 °C.

Water. In the wild they come from different water (pH 4.6–6 vs 7–8.5). Captive-bred fish often adapt; a stable pH matters more than an exact number.

Temperament and size. Cardinal tetra is peaceful and grows to 3.5 cm; Molly is peaceful and grows to 8 cm. Both use the mid of the tank, so give them room and cover.

Tank size and groups. Plan on at least 30 US gallons, the larger of the two cautious minimums. Keep Cardinal tetra in a group of 8+. Keep Molly in a group of 3+. A starter mix of 8 Cardinal tetra and 3 Molly in 30 gallons uses about 50% 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: both are calmer with cover. Plants and floating cover make shy fish come out more, not less.
• 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 Cardinal tetra

These pass every rule with Cardinal tetra: Bronze corydoras · Cherry barb · Chili rasbora · Ember tetra · Harlequin rasbora · Honey gourami · Neon tetra · Panda corydoras.

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.