Can Harlequin rasbora live with Swordtail?

Temperature. Harlequin rasbora does best at 22–25 °C (72–77 °F) and Swordtail at 22–27 °C (72–81 °F). They share 22–25 °C.

Water. Their pH ranges overlap at 7–7.

Temperament and size. Harlequin rasbora is peaceful and grows to 4.5 cm; Swordtail is semi-aggressive and grows to 14 cm. Both use the mid of the tank, so give them room and cover.

Tank size and groups. Plan on at least 40 US gallons, the larger of the two cautious minimums. Keep Harlequin rasbora in a group of 8+. Keep Swordtail in a group of 3+. A starter mix of 8 Harlequin rasbora and 3 Swordtail in 40 gallons uses about 73% 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 Harlequin rasbora

These pass every rule with Harlequin rasbora: Betta (male) · Black skirt tetra · Cardinal tetra · Celestial pearl danio · Cherry barb · Dwarf gourami · Ember tetra · Endler's livebearer.

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.